Facebook groups. Everyone likes them or eveyone hates them. I personally prefer pages and not groups. That is just a personal preference more then anything else.
One of my biggest complaints with Facebook groups is ANYONE can add you to a group without your permission as long as they are your Facebook friend. This is both irritating and a violation of privacy. You should have control on which Facebook groups that you join. I would rather Facebook send an invite and then ask me to choose if I want to join the group
This is a policy that Facebook needs to change. On a regular basis I leave groups that I have been added to without my consent. Lately I have averaging a couple of groups that I leave on a weekly basis. Most of these groups are either spammy or ones I am not interested in.
Facebook if you are serious about privacy you need to change how people are added to groups NOW