I explained the situation here - http://www.bobatkins.com/photography/photo_gear_buyer_beware.html
Basically I don't get to pre-approve which ads Google serves to me, so I can't stop such ads from appearing at least once. If I see such an ad and I can identify the advertiser, I can put them on my blocking list (I can block up to 200 domains from advertising), but I can only do that if I see the ad. Since I can't possibly view every ad that shows up on every page on the site, if an ad just pops up once or twice, odds are I won't see it.
If someone reports a bogus ad (along with the domain that it directs you to). then I can (and do) add it to the blocking list. That's about all I can do, since without the advertising from Google I couldn't really afford to run this site and spend the time on it that I do. Luckily most of the Google ads are from reputabl;e dealers. It's unfortunate that the photo retail trade has an unusually large percentage of "rip-off" stores which sometimes get their ads posted here. The only upside is that it costs them everytime you click on their ads and if you've read the articles on this website you're not going to be fooled by their "bait and switch" schemes.
FYI I just added techondigital.com
to my blocking list. They were advertising the XSi for $279 and they're clearly not a store I'd recommed anyone deal with. The block list usually takes a few hours before it gets read by Google and ads start being blocked. That's another one down, but I'm sure there will be more.