What are the most common things to test in a new site?
For instance to prevent exploits by bots, malicious users, massive load, etc.?
And just as importantly, what tools and approaches should you use?
(some stress test tools are really expensive/had to use, do you write your own? etc)
Common exploits that should be checked for.
Edit: the reason for this question is partially from being in SO beta, however please refrain from SO beta discussion, SO beta got me thinking about my own site and good thing too. This is meant to be a checklist for things that I, you, or someone else hasn't thought of before.