Tell me why you aren’t going to be the next Friendster.”

– Venture capitalist David L. Sze’s 2006 litmus test for entrepreneurs who claimed to have the next MySpace.

If Orkut is the Facebook of Brazil, then Friendster is the Orkut of Asia. The company, which created the social- networking market only to forfeit it to Myspace and Facebook, is apparently doing quite well in Asia. So much so, that it’s used its success on that continent to secure some new venture funding and a CEO with a Google (GOOG) pedigree. In a statement proclaiming itself the No. 1 social network in Asia this morning, Friendster named Richard Kimber, Google’s Managing Director of Sales and Operations for South East Asia, as CEO. The company also said it has raised $20 million in new venture funding from DG Ventures, Kleiner Perkins Caufield & Byers, Benchmark Capital, DAG Ventures, and the Founders Fund. Friendster plans to use that money to hire up and bolster its presence across Asia, specifically Singapore, the Philippines, Malaysia, and Indonesia.

Perhaps, we’ll see that Friendster movie yet–though I still can’t imagine a worse concept.

Which begs the question: Is Facebook nearing its saturation point? Is enthusiasm for the social-networking phenom finally wearing off? Have we all been spammed by the ironically named “Funwall” one time too many? Are the site’s privacy issues finally taking their toll? Or are its zombified members too busy seeking human flesh to bother updating their profiles?

Or were they simply on winter holiday?

That last scenario seems the most obvious explanation. December and January are the months at issue here. And Nielsen’s figures show that there are 712% more Facebook users than a year ago. Still, this is the first drop the firm has recorded in Facebook’s user numbers in the U.K. since the site became large enough to track. There wasn’t a similar drop in usage last year. Or the year prior. So maybe there is something more here. The early beginnings of a long-term erosion, perhaps?

“One month of falling audiences doesn’t spell the decline of Facebook or social networking,” said Nielsen’s Alex Burmaster. “However, most of the leading social networks are less popular in the U.K. than they were a year ago. It was inevitable that early growth rates couldn’t be sustained and the larger networks have been plateauing over the last few months.”

Seems the leading social networks to which Burmaster refers were also less popular in the U.S. According to the latest stats from comScore, Facebook attracted 33.9 million unique visitors stateside in January–down 2% percent from 34.7 million in December. That’s a decline of approximately 800,000 users. Again, this drop could also be chalked up to Seasonal Facebook Defection Disorder. Or not. After all, it’s not like we haven’t seen this sort of thing before. Remember Friendster?

UPDATE: Facebook disputes Nielsen’s metrics. “The number of users for Facebook continues to climb in the U.K.,” the company said. “Our internal monthly active user numbers rose between December and January in the U.K. and are now at more than 8.3 million. Facebook tracks active monthly users, rather than registered users or unique visitors. Active users reflect those who have used the site in the past 30 days.”

OpenSocial, as Google has named it, is a set of common APIs (application programming interfaces) that will enable developers to write applications for a broad range of Web sites and services without any individual customization. Think of it as Facebook CEO Mark Zuckerberg’s “social graph” but writ large.

And while some might smirk at OpenSocial’s initial roster of participants–LinkedIn, hi5, Ning, Friendster, Plaxo and Google’s own “big in Brazil” social network Orkut–it does include a few big names: business software makers Salesforce.com and Oracle. Oh, and Google. Which, as TechCrunch’s Erick Schonfeld points out, already has much of the critical mass it needs to push this effort forward: “Google already has so much data on you, depending on how many Google apps you already use. It just needs to bring everything together. … Over time, Google will connect all of these together in different ways, along with data about you from other social services across the Web, and give developers access to the social layer tying all of these apps together underneath. The real killer app for Google is not to turn Orkut into a Facebook clone. It is to turn every Google app into a social application without you even noticing that you’ve joined yet another social network.”