One of my users let the cat out of the bag and told me they were using one of my free apps, which is monetized by ads, but they were blocking the ads with an ad blocker. The
This is an extension of a previous answer. The user has informed me that the app they are using is called AdFree Android. It can be found on the market. The app says it works by "nullifying requests to known hostnames serving ads."
I suggest that if you monetize any of your apps with ads, you check at startup for this program and give the user a nasty message, then terminate your app.