Recently I just had an interesting discussion in a forum. It is about high paying keywords. It is interesting that there are keywords about online gambling ,casino online or online slots that included in the top position of high paying keywords. The top keyword price bid reached $21.29. There are also another high paying keywords about other topics related to attorney like dwi attorney, federal criminal attorney, auto accident attorney.

Back to Google AdSense, if we see the Google adsense policy, sites that include this topic are not eligible to join the adsense program:
Violence, racial intolerance, or advocate against any individual, group, or organization, Hacking/cracking content, Illicit drugs and drug paraphernalia,
Pornography, adult, or mature content, Gambling or casino-related content.

For more information about google adsense policy you can read it here: https://www.google.com/adsense/policies.
And here is more link about google adwords content policy : https://adwords.google.com/select/contentpolicy.html

Some friends of mine tried to sign up for google adsense program with their gambling or poker web site, and they all never got accepted. Another friend tried to apply the program using another web site, and once they got approved they sneaked the code into the gambling site. This action even more dangerous, because you can get your account banned. Having a gambling site is really fun and it also has good chance to gain a lot of traffics, but how to monetize the site is also different.