Could not agree any further.
Social networking - outside of posting on here because I'm a sci-fi fan - generally isn't interesting me because the only purpose for me
to use it is to make money. And facebook IMO isn't a way to network with people and expand your contact base with business professionals.
Linkedin however I find useful in terms of networking with other business professionals and enbables me to make more money and be more effective at my job.
I've never needed either.
I had both Facebook and LinkedIn. Facebook seemed to be a complete waste of time. The people I would chat with I had on my Live Messenger, or SMS. And 90% of my "friends" were old coworkers or people from College that never talked to me at all (so why add me as a "friend" then?)
It seems to be a huge popularity contest that I could fucking care less about.
As for LinkedIn, I tried it and it seemed to be a waste of time for me as well. I've never needed to network to find work. Unfortunately very few people I know were in positions to help me further my career. Those who could help out usually weren't people I was close to in anyway.
In the end, I found LinkedIn was simply a security risk where tons of my private work history was up for grabs by anyone. So I ended up deleting both accounts permanently and never looked back.
I laugh at all the people facebooking on the bus on their iPhones and Blackberries. I either read ebooks or play games on my iPad, and find that far more entertaining.