First it was the omnipresent Brown Bailout ads. Then today it was Groupon. No, I don’t think people will click on an ad if Adsense is allowing the advertisers to carpet bomb the website.
When viewing an individual post on my main blog several times day, a Groupon ad was both in the post itself and in the side bar.
Advertisers can put the url of the ad site into competitive ad filter, however Adsense needs to manage this better. Endless repetitions of the same ads lowers Google’s income too.