Social Networking

As someone involved in public relations, I have recently been experimenting with various social media networking sites (Twitter, LinkedIn, PR Open Mic, etc.).  They're all easy enough to create profiles on and find people to connect with, but I've been wondering how "effective" they truly are for networking (aren't PR people always trying to prove how effective something is?).  I feel like people go through the motions with these websites, accepting "friend requests" or searching for coworkers but few people really get much out of these connections.  I just read a post on PepperDigital's blog (a division of one of the companies I interviewed with this past week, Peppercom) that seemed to share my sentiments - these websites are great in theory but are more passive than anything.  

I wonder if these websites will be more widely used and effective as more people get involved in the social media world?  It's interesting to be in the generation that gets to watch all of this evolve first hand, and I can't help but wonder how different things will be in 5 months when I graduate.