With Clearwire struggling to build out a next-generation network that will go up against Verizon Wireless (VZ) and AT&T (T) for future mobile customers, Sprint has little choice but to throw more money at it. But it’s not alone in doing so. Fellow partners Comcast (CMSCA), Time Warner Cable (TWC), Intel (INTC), Eagle River Holdings and Bright House Networks are also making additional investments, though together they total only $500 million.

Oddly absent from this list is Google (GOOG), which participated in a May 2008 investment round that pumped $12 billion into Clearwire but has evidently decided to sit this one out. Said Google spokesman Andrew Pederson: “We have already made a significant financial investment, and at this point we think the best way we can continue to add value is through continued product and strategic cooperation.”

One wonders if the shared mission of which the two companies boasted when the deal was announced has somehow changed in the ensuing year.

BoomTown got the ball rolling by making a visit to Twitter HQ bearing pies. During a video tour of the premises, Biz Stone discussed rock stars and booze, and spilled the secret of the strange green deer. Later, co-founders Stone and Evan Williams were customarily nonspecific in a conversation about their revenue plans, and BoomTown was a little bit horrified to have become one of Ashton Kutcher’s million-plus followers–maybe even the one that put him over the top in his race with CNN to hit the seven-figure mark. Still on the celebrity tip (but off the Twitter one), BoomTown took a moment to appreciate the self-deprecatory stylings of Lindsay Lohan’s eHarmony spoof and to embed the video on AllThingsD.com. Finally, was there anyone this week who missed Susan Boyle’s virtually instant stardom on “Britain’s Got Talent” via Google’s (GOOG) YouTube? BT took a look at the journey the story has taken from television to Internet, back to television and back to Internet again.

Back to Twitter, MediaMemo took a look at its amazing growth as a service and as a phenomenon–the “hockey stick,” as one early investor describes the company’s trajectory so far. MM also looked at a study from the USC neuroscience group that says despite all the hype–or maybe even because of it–the human brain just isn’t built to digest information at Twitter’s pace. In the world of cable this week, just as folks were wondering whether Congress will stop the cable companies from charging by the byte, Time Warner Cable (TWX), one of the key players in the drama, backed away from its plans to do so. MediaMemo followed that story as well.

In this week’s Personal Technology column, Walt Mossberg took a look at the latest version of Apple’s (AAPL) MobileMe, and while he found it to be a big improvement over the product launch from last summer, it’s not without limitations. In Mossberg’s Mailbox, Walt answered questions from readers about displaying emergency contact numbers on a locked cellphone and the security of running Windows software on the Mac. And in Mossberg Solution, Katie Boehret took a look at Gwabbit, a program built to mine emails for contact info.

More next week.

With $3.2 billion in investments from the likes of Comcast (CMCSA), Intel (INTC), Time Warner Cable (TWX), Google (GOOG) and Brighthouse Networks, the new Clearwire has quite a few masters to serve, though CEO Benjamin Wolff insists none will have a direct hand in the company’s operations. “We have very little in common with a joint venture,” he said during a conference call on Monday, claiming Clearwire’s investors have no say in the timing of network launches. Hard to believe that’s the case when a $1 billion investor like Intel holds a seat on Clearwire’s board. But if it is, Wolff’s lucky. Because with Verizon (VZ) and AT&T (T) planning to bring a competing fourth-generation network called LTE (long-term evolution) online in the next year or so, Clearwire can’t afford any unnecessary distractions lest it lose that all important time-to-market advantage. “The credit markets are lousy” will only work as an excuse for slowed deployment for so long …

The deal, which has been approved by both companies’ boards, calls for Time Warner Cable to pay a hefty $10.9 billion one-time dividend to shareholders. As parent company, Time Warner (TWX) will pocket $9.25 billion of that payout.

It’s a flashy move for Time Warner’s new CEO Jeff Bewkes, who’s been hard pressed to reinvigorate the company’s stock price. “After the transaction, each company will have greater strategic, financial and operational flexibility and will be better positioned to compete,” he said in a statement. “Separating the two companies will help their management teams focus on realizing the full potential of the respective businesses and will provide investors with greater choice in how they own this portfolio of assets.”

That’s all well and good, but how does Time Warner plan to realize the full potential of a $9.25 billion payout? By buying a company or two, perhaps. “Our share of the special dividend will clearly enhance our financial flexibility,” Bewkes said during a conference call this morning. “… We’re looking at all of the usual uses of capital, including returning capital to stockholders, including disciplined acquisitions and including investing further in our business.”

The alliance will see the four cable and tech companies investing $3.2 billion in the nationwide wireless network that Sprint and Clearwire have been struggling–with profound unsuccess–to roll out. Comcast (CMCSA) will contribute $1.05 billion, Time Warner Cable (TWX) $500 million. Intel (INTC) will invest $1 billion, Google (GOOG) about $500 million. The new venture will be majority owned by Sprint, but it will take the Clearwire name and be run largely by Clearwire execs, among them cellular industry pioneer Craig McCaw.

For the cablecos, which have yet to settle on a clear wireless strategy, the deal is a quick and dirty way to establish the high-speed wireless network they need to compete with telcos like AT&T (T) and Verizon (VZ). For Sprint and Clearwire, it’s a chance to make their non-starter of a WiMax network viable and something happy to talk about when conversation turns to Sprint’s stock price, which has fallen nearly 60% over the past 12 months.

That said, the deal is not without its problems–top among them WiMax itself. As Craig Moffett, an analyst with Bernstein Research, explained in a note to clients earlier this year, the 2.5 GHz spectrum upon which Sprint and Clearwire are building their network isn’t nearly as good as the spectrum Verizon and AT&T just purchased in the FCC’s 700 MHz auction. “Serious questions remain about penetration through walls and windows,” Moffett explained. “Elsewhere in the world, operators have also raised questions about WiMax’s real-world bandwidth, latency and non-line-of-site coverage. How competitive the offering would be versus Verizon’s or AT&T’s planned LTE broadband service therefore remains to be seen.”

That it does–though there have been some indications that it may not be quite up to par. Speaking at an international WiMax conference in Bangkok in March, Garth Freeman, CEO of Buzz Broadband, Australia’s first WiMax operator, described the technology variously as a “disaster,” “miserable failure,” and a standard “mired in opportunistic hype.”

So will that prove true for Clearwire as well? We won’t know for some time. Building out a massive network like this will take some doing. “We’ll likely to see early trials in 2010, but a full-fledged build-out will take longer,” Clearwire CEO Benjamin Wolff said during a conference call this morning. “Building faster is a matter of logistics. The build plan we’ve laid out will be one of the largest and fastest build-outs ever done. We have the capability to do it, but it’s a massive undertaking.”

Revenue at the AOL unit slid 23% to $1.1 billion, with much of that decline stemming from a steep 28% drop-off in dial-up subscribers. Ad-revenue growth slowed markedly, rising just 1%. Disappointing news for Time Warner (TWX), which has been mulling the possible sale of AOL. With the MicroHoo merger on the horizon, the field of suitors for the division could narrow by two very quickly.

That said, today brought with it good news for Time Warner as well. The company reported first-quarter earnings that were largely in line with analyst expectations and announced plans to spin off its cable operation. “We’ve decided that a complete structural separation of Time Warner Cable, under the right circumstances, is in the best interests of both companies’ shareholders,” Time Warner CEO Jeff Bewkes said today in a statement. “We’re working hard on an agreement with Time Warner Cable, which we expect to finalize soon.”