Later today, Perlman–former principal scientist at Apple (AAPL) and the founder of WebTV–will officially unveil OnLive, the online service with which he hopes to upend the $46 billion world-wide videogame market. Seven years in the making, OnLive promises to create an on-demand gaming experience that rivals those offered by dedicated videogame consoles. It’s capable of streaming even the most advanced, CPU-intensive games to television and computer–Macintosh or PC–without lag or a reduction in quality. “We’re providing you with the latest high-end titles, the exact same ones you would see at Target or Best Buy, in the same release windows,” Perlman told USA Today. “But what is really cool is you don’t need any high-end hardware to play them. There’s no physical media. It’s an all-digital platform. You never need to upgrade your equipment at home.”

A compelling proposition. A potentially disruptive one too, if OnLive is able to deliver it with the reliability and ease of use it promises. Said IDC analyst Billy Pidgeon, “It’s a good idea and has potential, but the thing I need reassurance on is being able to deliver this over the network. In games there’s no wiggle room–when you press a button to fire you want to fire,” he said. “But if it works, this could be a disruptive.”

Announcing the debut of Last.fm’s “unprecedented” on-demand music streaming platform, Jones–in a moment of Zuckerbergian grandiosity–proclaimed:

Today we’re redesigning the music economy.”

Which will no doubt come as a bit of a surprise to Apple, and Real, and Amazon and, above all, Imeem, which announced a similar ad-supported service last month.

To be fair, Last.fm’s free on-demand service seems a bit more compelling. Certainly, the CBS-owned site is the only one among the few to offer access to music from all four major labels and a host of independents to anyone willing to stare at an ad for while. And providing complete album streams on a “try before you buy” basis is truly a nice touch.

Still, Last.fm does have one significant limitation: You can listen to a track no more than three times unless you agree to pay for the subscription version of the service or purchase it from an affiliate. Will that be a deal-breaker for the average music fan or a good reason to buy your music through Last.fm, rather than iTunes? Hard to say. “The free-music-on-demand field has been a tough one, with many announcements but few real entries (consider, for example, the often-delayed Qtrax and vaporous Mashboxx),” notes the Los Angeles Times’s Jon Healey. “With CBS’ backing, Last.fm might be able to search longer for a workable formula than the typical start-up. But at some point, it has to find a way to pay the bills.”