Pity News Corp. (NYSE: NWS, NWS.A) spent half a billion dollars to buy MySpace, whose profitability rests solely on the attention span of teenagers. Google, Inc. (NASDAQ:GOOG) should take a lesson about its purchase of YouTube. Get your money while you can, because teenagers move on to the next cool thing with lightning speed.

Yuki Noguchi from The Washington Post, wrote last week that the popularity of MySpace, THE required teen social spot last year, is already plummeting in favor of Facebook. Not only purchasers, but advertisers as well, are betting they can predict the social behavior and coolness factors of teens. There aren't enough regression analysis models in all of econometrics to account for such irrational variables.

Xanga, the precursor to MySpace, was THE biggest site in 2003, averaging over 90 minutes per visit per user as teens developed and edited their online profiles or scoped out the profiles of others. In September 2006, the average viewing time of a Xanga profile was 11 minutes. The story is the same with Friendster, which averaged almost two hours of user time per visit in October 2003. In February 2006, average viewer time peaked at just over 3 hours. By September 2006, average viewing time was 7 minutes.

MySpace has already showed the beginnings of a decline in average viewer time. In October 2005, the average viewer time was almost 2 and a half hours. By October 2006, average time had slipped to 2 hours. The up and coming social network site is Facebook, which is still showing increases in average viewer time, now up to 70 minutes per visitor per month.

Among teens, there is very little in the way of brand loyalty. Mostly, teens crave innovation and new experiences within the confines of group experience. Given the increased scrutiny social network sites encounter from teachers and parents, as well as recent negative publicity caused by predators using MySpace, investors and advertisers can expect the next replacement social network site any minute. Too late, it's gone.

MySpace may be the space of the moment, receiving praise, aplomb and (most importantly) generating traffic to Google in ever-greater numbers, but it's not even the middle of the social network craze. Really, the whole social network effect, as a theory and a technological practicality, started with the personal web sites of the early nineties. Personal web sites beget blogs beget networking sites like Orkut and LinkedIn beget MySpace, AIM Pages, YouTube, and whatever's to come next.

Thanks to a effort by white shoe management consultancy McKinsey to get the great minds of YouTube, Yahoo! and the like together with the old garde of the gigantic media (and I'm asking myself, and Aaron Cohen of Bolt Media, who was interviewed as a person of knowledge for the Financial Times piece: whither side of the old/new divide does Time Warner fall?), social networking is now coming into the good graces of the giants of Wall Street and Hollywood and Madison Avenue and all those places where fashion and money meet the people.

Robert Young, writing for GigaOm, calls MySpace the "it girl," and describes the infatuation with "her" and her groupies this way: "nearly every media company and venture capital fund on the planet is out on the dance floor stumbling over one another to see if they can identify the next breathless social networking beauty."