I recently got a message on Facebook from a family member. She wasn't sure why we weren't friends already, but I really needed to accept her friend request right away.
I declined it. The thing is, we've been friends twice before, and I've unfriended her twice before.
I'm extremely selective about the people I befriend on Facebook and follow on Twitter. I don't think I'm special -- I'm not popular and I'm no web socialite, I'm just trying to keep things manageable.
Consider Dunbar's number. Also consider that I'm trying to manage my very, very valuable attention. (Attention: it's the new 'time', as in 'Time is Money'.)
Let's say you and I are friends on some social network and you happen to play games or run exercise apps that post status updates on your behalf. I'm sure you're having a great time, but those things totally clutter up my feeds with intrusive garbage despite my account settings, so our friendship just can't last.
Sorry -- it's not you, it's me. (That last part is completely untrue -- it's all you -- but sometimes it feels nice to act apologetic.) I've unfriended/unfollowed more than my fair share because of pseudo-social advertisement, and I'm really not ashamed of it.