In the past I have talked about why Project Wonderful is a such a good website to advertise on a relatively small scale. One of the reasons is because the cash value of the ad space is very low compared to other ad networks, so a little money goes a long way. However, for publishers, that means less revenue. On Think Before You Think, I publish ads from both Google and Project Wonderful. Although I could probably get more revenue from publishing ads exclusively from Google, I still choose to publish Project Wonderful ads as well. Why, you ask? Mainly two reasons:
1. Each user has a single account for both publishing and advertising. That means once you have gotten some ad revenue, you can use it directly for advertising. I find this convenient - I never have to think about putting money into the account for advertising, I only use the revenue. Since advertising is cheap, for me it is one of the best ways to use those accumulating pennies.
2. Publishing ads on Project Wonderful serves as a form of advertising in itself. Advertisers do their own targeting, and may check out your site to assess its relevance and ad placement, before placing a bid by hand. That means you get visits, and especially if the ad is particularly well-targeted, the advertiser might take interest in your site. I say this because there are numerous webcomics that I have found by advertising on them, and continued to read.
You can assess for yourself whether these advantages make it worthwhile to publish Project Wonderful ads. It seems to me that even having one small ad space would reap these benefits. Also, I just think it's cool to give other comics a chance to advertise on my site by choice, and they can't do that with Google.