Make clear which profile data is visible to whom
On my profile are fields 'website', 'real name' and 'email'. I deliberately left the 'real name' field blank and when I signed up, Stack Overflow promised not to publish my email. Yet there it is :(
Edit: Apparently profiles look different when logged in. Some fields in that list are public some are private. I think they should be marked private rather than displayed the same as the public fields.