Itís not about the users, and itís not about deception Ė itís about keeping the advertisers happy.
If they sell stuff to people who maybe didn't see they were clicking on an ad, thatís fine. Ads that are not obviously ads are much older than the Adsense or the Internet. And I donít have a lot of doubt that Google has statistics to show that blending (done properly) is good for business, benefiting their publishers, advertisers, and themselves. (And the users are maybe pretty happy with all the cool stuff they bought, but thatís a secondary consideration.)
But if you send advertisers useless traffic, or if you dilute their branding efforts, they wonít like it.
Iíve got some experience in the advertising business, so this may be second nature to me. But I think if you just look at this from an advertiserís perspective, it should all make sense.
Owner edit: Changed a misleading sentence.