Those who misuse the website.

1) Notices that say "This site/page is under construction."

That's so amateurish. At the very least hide the page or don't publish the page/site until everything is complete.

2) Compulsory surveys - these are an absolute No-no.
No objection if I'm asked to help by participating in a survey and thus have a choice but where the survey is thrust at you - I just log out or close the page.

3) Sites with nasty fruitcakes - We've had a few and regulars will know that some established contributors have left AP as a result.