The FB Dilemma

What to do when people you work with want to “friend” you on facebook? I try to not blend my work and personal life. It is why I never disclose where I work anywhere online, here or FB, etc. With the exception of a few trusted work friends from my Michigan days, nobody from work knows about my little online ramblings home right here.
There are a few people from work I genuinely like but still it crosses a line. And you run into the problem of “friending” those that you like and then having others at work who are their friends discovering you on FB and wanting to be friends.
So I have made rules for “friending” people on FB. No coworkers, with the exception of one or two from my previous work home in Mich. And only being FB friends with people I would actually want to sit with and have a meal and the conversation that goes with.