How many block need to remove someone from facebook?

[Milind]

[Ann]

Just one block needed to keep them from contacting you. You don't remove them, but you won't see them much unless they post on someone else's page.

[Suman]

You have your own reasons for blocking, reasons may range from annoying users to as simple as not liking their face. A person may get blocked any number of times, but facebook will never ban that person, rather it might put some extra restrictions, like no comments, or wall posts, etc.