[lucumo]

You should write that bookmarklet. As a site owner, I can tell you I'd probably ignore it if it's only one person, but if several people are complaining, I'd look into it and discuss the problem with one or a few of them. And I would be grateful for the feedback.

Constructive feedback is always good. "Your ad in location XY is loading very slowly." "The ad for product Z is misbehaving and causing a redirect/hang/whatever." As long as it isn't annoying comments like "I don't like ads, you should remove them" or "It moves. Can't you just use ads that I don't notice?" Those are pointless, because they hinge on the concept that ads are fine as long as nobody sees them, which goes against the whole point of ads.