Might as well throw in my two cents
Another board i am a member on ran into financial trouble and they turned to adsense. To be perfectly honest it hasn't made much of a difference at all. They did it in a very unobtrusive fashion and it hasn't degraded the quality of the site at all. They used adsense for about a year and then moved on to other forms of revenue. They now get retailers to pay for ad space and again it works very well.
~DEATH be not proud, though some have called thee Mighty and dreadfull, for, thou art not so, ~