What I hate most is the scrolling. I admit that may be an Opera issue, but compared with the Chrome and Firefox memory issues, I'll live with the scrolling. I don't expect it to be bothering me for too much longer anyway.
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 .