Those ads are highly intrusive - probably the best reason yet for abandoning the mouse/cursor interface in favor of an iOS-like touch based UI. It's incredibly annoying to have to use caution when moving your damn cursor around the screen. Whose computer is it anyway?
If you click on the "?" icon (once the ad has loaded) you can specifically disable it, but only for that page, so it's not useful.
Complain all you want, but websites love Kontera. All you can do is avoid those sites, don't patronize their advertisers, and maybe even tell 'em why.
Advertisements are not going away. Revenue has to come from somewhere, all the more reason I like iAd. If we must tolerate advertisements in exchange for "free" content, let Apple control their delivery. At least they'll do it with elegance.