What topics won't Adsense serve ads for?

Some page subjects generate only PSAs

[diamondgrl]

Does anyone know of topics that Adsense seems to avoid like the plague?

I have noticed, for example, that if a page is largely themed on weapons of mass destruction or terrorism, for example, Google will only serve up PSAs. Doesn't matter, I don't think, what other keywords might be on the page. If Google senses too much focus on terrorism, it won't serve an ad.

Anybody else notice that? What other topics are not okay?

[Jenstar]

Various threads on stop words [google.com]

There are plenty of examples in the threads we have had here on stop words. The filter is also flexible, so what is fine today, could result in PSAs tomorrow.

[diamondgrl]

Thanks!