Google not allowing adsense on certain sites?

Have any of you heard of a problem where google is not allowing ads to be shown on some sites? I don't mean like porn sites, or hacking or anything like that either, but like legitimate websites. I haven't exactly had my ear to the ground recently, so please forgive me if I've blatantly missed what to many of you may be completely obvious LOL.

Well if your sites are excessively spammy, or are if you have adsense on sites that are in linkfarms etc that could lead to getting and adsense ban

Yes.
Your site could be blocked from displaying adsense if the site had violated adsense terms in the past. Also check yours robots.txt file. If you block the adsense bot, that could also be a problem.
-Neo

Mainly I was referring to sites that are about a product or group of products, that have good content, and adsense ads. No pictures, no widgets or anything else. Would your replies still apply in that regard?

Also, to be clear, assume the subjects in the above questions did not actually have their accounts banned, it's just that google refused to show ads on some of their sites.

Let us say you are running adsense on many sites without any problem. Now you decided to try something new and bought a new domain, sonydsct900.com
You have good content about the Sony DSC-t900 model with no pics and no affiliate links, but just adsense.
If a person from Sony visits this site and then report to google that your site is in violation of their copyright, google will stop displaying adsense ads.

You might not get your adsense account banned for this because you are not violating any adsense TOS.

There's some certain situations where google can banned you
-You spam your links too much, or you accidentaly submit your site to a directory that spam your links
-You send fake traffic
-You have a very high CPM and they get suspicious
-You use xrumer too much