I got an interview because of LinkedIn. I basically connected with a guy who worked at a company I wanted to work at, and we talked a bit, then we met at a tradeshow and the next day I had an interview scheduled. That wouldn't ever have happened without.
It of course depends on what business you are in, or want to get into. But it doesn't hurt to have a LinkedIn profile, or a profile at more industry specific sites. Sure, you have to deal with recruiters and all of those bullshit accounts, but I think it's worth it for certain industries.