The folks at Lionel might as well just release the thing online I mean it's showing up everywhere. Unless you are willing to enforce the no catalog before the online release then all the secrecy is a moot point.
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 .