Judging people every day

Not that long ago you needed to make hard decisions once a year: to whom to send Christmas cards. Who belongs to your (extended) family, are your neighbours worth a card, do you still want to greet your old class mates or colleagues that you saw 10 years ago and what about people you never see: the postman, your landlord.

Now you need to judge people every day: to accept an invitation or not in one of those social networks. E.g. Facebook was meant for friends and LinkedIn for colleagues, right? Now I got FB invitations from people that are not in my phone's contacts and from people that I have never seen in real life. Sounds like a close friend? How about people that share the same office but with whom you never worked or even talked, you know their name but that's it - can you really consider them as your colleagues in LinkedIn?

I'm a friendly person and sometimes making these decisions is very difficult. If i accept an invitation from x that I don't know that well do I then need to invite y that I know much better? If I reject an invitation do I need to explain why I did it? If I have way too many friends in a system, I can't actually follow them all - a recent study was saying that you can follow "only" about 150 persons. And then the privacy issue: I don't want to share the same stuff with my friends and my so called friends. I wrote earlier about my blogs: I have several of them and their themes are tailored for the audience. At the moment I can't do the same in the social networks - or should I create several accounts? Not very handy...

Any comments? Do you find it easy to make these decisions?