My experience of recruiters is mostly good. I spend almost no time saying no to offers that I don't like. For offers that might be good, I have a better negotiating position than if I applied for the job - I still have my current job, so they have to make a really good offer, otherwise I won't switch.

I am mostly contacted on LinkedIn, and I think, on balance, that it works well there. I've written about it here: http://henrikwarne.com/2013/08/21/linkedin-good-or-bad/