I don't think so. Take a look at this interesting discussion of two big US retailers (Target and Wal-Mart) using Facebook. Social networking is here to stay. The real question is which type of social networking tools will you use and for what purposes? Maybe a quicker way to say it is this 'Who are you where?"
Here's more on this topic - http://blogs.msdn.com/industry_social/archive/2008/03/17/social-networking-in-retail.aspx
Even more interesting for developers I think is this fact - not only must we contend with different systems, but, more importantly, different languages as we are asked to work in these disparate environments. The purists out there 'just want to write code', but those of us who have a more practical bent are becoming more and more interested in leveraging visual programming tools - whether they be built into the IDE (for example Windows Workflow), or appear as new types of IDEs (such as PopFly).
Check out this guy, Gary Vaynerchuck from Wine Library TV - he gets it and he's laughing all the way to the bank. BTW...I recently met him in person - he's a character!
What do you think? Which social networks will you / do you write applications for now?