If you value privacy or are tired of seeing ads that seem rather stalker-ish on your Android device, Google now lets you opt out of their targeted ads. Applications that use AdMob or AdSense (i.e. Angry Birds) will no longer track your preferences and display stuff you might be more interested in than random ads. Google explains it as follows:
If you opt-out, your device identifier information will not be used by Google for advertising going forward and you will not receive ads based on your interests or inferred demographics.
You can read the more details about how targeting works in the source below, or you can just swing into your Market settings and uncheck one box to get rid of targeting ads altogether.
Image: Google AdMob
Source: Google AdMob