Mixed saftey
Be able to block users from sending email to advertisers. If a email is banned it can not go to the user for example ban a IP to send more then 4 emails a 30 min or something.
Block so you can only report a post 1 time like digg.com
Save the IP and as much info as you can when someone sign up so you can block people from having more then one account.
Hide the emails better as talked in the bug forum.