Say Uncle just got a nasty-gram from the boys at Google telling him to basically kiss off because his site mentions guns...
While reviewing your account, we noticed that you are currently displaying Google ads in a manner that is not compliant with our policies. For instance, we found violations of AdSense policies on pages such as thegunblogs.com.
As stated in our program policies, AdSense publishers are not permitted to place Google ads on sites with content related to certain weapons and weapon accessories, such as firearms, balisongs, butterfly knives, and brass knuckles.
As a result, we have disabled ad serving to the site.
The funny thing is that I noticed that where Goggle has problems with sites mentioning guns, they have absolutely no qualms with taking money from advertisers that sell things such as air-guns, "gunshot ringtones", and even GUNS (eBay ad)! (Taken FROM Say Uncle's site)
Not only do they take money from those advertisers, They have no problem advertising sexual items or even prostitution!