yeah why not. there is nothing wrong with that. I am using them both for one of my sites and earning from both.
DON'T listen to these guys! But by all means try it if you like and some guy like me will come along and buy the entire adsense block and stick there ad there, and steal all you're traffic and profit from it.
Hi, You can use clickbank and google adsense no problem at all. Make sure you get the traffic coming to you site thought and you should be fine.
try it out. You gotta experiment with everything and see which way yuor sites/niches earn better. Goodluck in your earnings.