This extremely important and busy topic goes into chapter two as "Super Tuesday" dawns. Ive bumped in the last ten posts or so from part 1 to get the thing rolling..
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .