I use different social networks in different ways. If I don’t add you on Facebook, this explanation might help.

I don’t want to offend anybody, but I like to have a well-defined target group for each network I’m a member of. This cuts down on the decision-related stress I face from using these systems.

Google+ and Twitter. Feel free to follow me. I may follow you back, but don’t be offended if I don’t. I tend to follow people according to my current research interests.

Facebook. I reserve this for family, old friends and people who live locally to me. I do not add any professional or business contacts here.

LinkedIn. I accept connection requests for anybody that I’ve met, even if it’s just by phone. Sometimes I accept requests as a “I’d like to meet you” signal, but rarely. I mostly ignore messages from people I don’t know.

Foursquare. I only accept connection requests from friends who would understand if I said “sorry, I can’t have dinner, I’m too tired.” Fortunately, nobody really wants to add me on Foursquare, so the decision rarely needs to be made!

As in regular life, I tend to prefer to meet new people online through introductions from existing friends and contacts.