Welcome to WebmasterWorld Guest from 18.104.22.168
Obviously, AdSense must be worth doing or no-one would do it, but my question really is, if I took part in AdSense, does it drive a portion of your business elsewhere? Or am I missing something here?
You can always block specific URL's of the ads displayed so you won't send customers to directo competitors, but because Adsense is so good everybody who pops up in your ad block should be a competitor. But, at least you get the idea.
If your site offers something for nothing, like information, shareware or whatever, then advertising is appropriate as an alternative to membership subscriptions.