its social and academic suicide. With the groups for your subject, a lot of useful questions are posted by your peers, and answered well by other peers. Facebook chat is kind of good in terms of talking with people especially in the first few weeks, if not in the long run. The truth is you will not be able to talk to everyone in person consistently, its not that i don't have the skills to talk to people in person-i can talk to people extremely different from me , and i have been commended on this-but yeah see it as you wish. Jokes are made on facebook about tagged pics etc, that give you common ground to talk about in real life.
i know it may sound abit sad, but a lot of juicy stuff goes on within the realms of facebook too. If you have an admirer, you never know, they might randomly add you and start talking from there, because they're not bold enough/too shy t approach you in person.
Theres too many reasons to have a facebook imo, i don't see what you gain in NOT having one. If you're not an active user, you shouldn't have problems with addiction, i say you keep it, but the decision is ultimately down to you.