how do you ban someone from facebook?

There is an option 2 block people from searching for you on facebook. If you access the 'settings' page (top right hand corner of the homepage) and scroll down to the 'block people' box you can enter the name of the person who you wish 2 appear 'invisible' 2.

If you block someone, they will not be able to find you in a Facebook search, see your Profile or interact with you through Facebook channels (such as Wall posts, Poke, etc.). Any Facebook ties you currently have with a person you block will be broken (for example, friendship connections, Relationship Status, etc.). However this would not stop the blocked person from opening another account in a different name!

If they're contacting them, then how did they get to be a friend in the first place, you have to agree to the request. Anywya, to stop anyone getting to your profile you can go into the security settigns and block that person

If several people report eventually they will be banned

dont forget though that if they have more than one e-mail address they can always sign up again, or create new e-mails etc