ResearchGate, Google Circles, Linked In -- useful or annoying?
Watergate, ClimateGate, ResearchGate?
I keep getting emails saying someone I know has "invited" me to join these "professional networks." In some cases, the person who supposedly sent the "invitation" denies it. So either the networks are outright lying (sending an invitation without any authorization by the "inviter") or they're asking permission to send an invitation, but in a way that it's not clear that's what they're doing. Like they translate "yes, I'm interested in what this person is publishing" into "this person is inviting you to join our network."
In my experience, most scientists are pretty willing to answer email questions (in their area of expertise, beyond what one could learn in 5 minutes on Wikipedia) and to collaborate when it makes sense, whether or not you're a friend of a colleague of a relative. So I don't see the point to these artificial networks. But I haven't used them, so maybe I'm missing out.