We were doing a maintenance on our database at that time. It was unscheduled, we normally do them on Friday from 1am-3am. And keep it as short as possible. It's normally about 1 hour per week though during the above time.
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 .