I don't know if it's just me (seeing as I'm relatively new to the Adsense program - I wouldn't be surprised) but during the first few weeks of using Adsense I enjoyed some reasonable profit. However, recently, I've noticed that what seems to be 99% of ads that appear on any of my site's seem to consist of 'Google Map' ads. Unfortunately the payout for these seem to be absolutely terrible. Perhaps it's just to do with the particular genre my site's comprise of? Both being based on a gaming theme. I'm just curious as to whether anyone else is currently suffering the same problem?
You have actually put your finger on the problem, the contents of you site determines the ads you get, perhaps if you want to position some of your pages for the more desirable keywords your revenue will go up.