if you received a lot of traffic, i'm sure google will to take it away from you, google means $G or $G$, remember this
There indeed are if one cares to look it up in Google or so. I haven't seen yet any for Adsense, but I've read enough about Google's to know they are quite protective of all their trademarks. There's at least one forum I know that uses Adsense in their domain. But that is probably because its owner somehow managed to secure permission. Dare to find out first hand?