First, the major social networks represent a significant portion, but still only a portion of all the conversations taking place in the social space.  Blogs, industry sites, help/discussion forums combined also offer social interaction which aren’t addressed by the current lock down.  Further, in the B2B world what’s happening on the later is arguably more relevant than the friendly chatter (of course that would mean missing the intellectual bliss of http://twitter.com/OGOchOCinco) anyways.  So yes, I’m sure the current block will have some impact, but there is still quite a bit of room for individuals to exert their social self.

Moving beyond that, I’d say the next large impact is the continual evolution of mobile.  I myself am far from an early technology adopter, but I’m excitedly awaiting the arrival of my new Motorola CLIQ with all it’s integrated social networking goodness.  As the social networks, and mobile, continue to advance more and more of the interactions will occur via personal mobile devices.  At some point, therefore, employers won’t be able to block access anyway, they will just influence the channel of consumption.

As one final point, I’d question how long the barriers will remain in place.  Resistance to change is pretty natural, but as more and more communication moves to the more fluid mediums of Twitter and messaging businesses are going to be forced to adopt.   There are examples of companies surviving or even prospering while thumbing their nose at convention (like Melissa & Doug where they don’t permit employee’s to have email) but they are more the exception.  A lot more companies have been successful embracing emergent modes of communication (2nd life aside…) and this will be no exception.

In conclusion, can the social wave be stopped?  My answer – absolutely not.  People are continually migrating the way they communicate to digital mediums and ultimately businesses will need to adopt, not suppress, their ability to communicate digitally to remain relevant.