Those ad units do more than make you money.
The Backend Of Internet Advertising: Your Ads Slow Page Load Speed
How I Make Money From My Blogs Via Advertising
How I make -- and don't make -- money from my blogs through advertising.
Torched From the Adsense Program (and Liberated from Pay Per Click Advertising)
Update, 23/01/2013: After submitting an appeal, Adsense re-enabled ad serving to this site. I'm not sure if I'm going to put the ads back up, please read this article and tell me your opinion in the comments below. I received the proverbial pink slip from Google's Adsense program a few days ago. They notified me [...]