it seems google just checks while opening an account. later checks r random and i think manual. like a frnd was pulled up for displaying two adsense banners on same page. but i c countless violations in other cases all the same. they need to pull up their socks on this one. aye they do.
If those sites are part of the Premium AdSense program, they seem to have a whole set of different rules from those in the regular program, including much more flexibility. This is also why you can see more than one AdSense ad block on a page of Premium partners. This could be why they have marketbanker running as well as AdSense. I can't recall running across both on the same page, but this could possibily be the reason.
Google seem to be quite vague about what constitutes competitive ads and what doesn't.
I sent them an email yesterday to ask if they had any issues with TCLA's non-text-ad products (which nevertheless incorporate contextual advertising).
Annoyingly they replied today with a canned response saying they don't allow competitive text ads, although they do allow affiliate links.
That didn't actually tell me anything I couldn't read for myself in the AdSense Terms of Conditions.
I wanted to reply and say "yes, but what about the question I asked you?" but evidently the responses are being sent out by an automated system which uses applied semantics to ascertain the topic of your question and then sends the appropriate canned response, so I doubt I'd have much luck.