You know what makes me sick?
You know what makes me jus' angreh? (cookie for the reference)
Intrusive, screen-obscuring, and/or noisy ads.
I do not mind normal ads that stay in their damn boxes. I understand it's a crucial revenue stream.
However, such ads as I have described, demonstrate a lack of respect bordering on outright contempt that the site has for its user base. This is why I often run with plugins disabled in Opera, and an extension to do the same in SeaMonkey or Firefox. That way, normal, unobtrusive ads may show. Malicious crap doesn't get the chance.