Google says, "Keep My Opt-Outs is an extension for users who aren't comfortable with personalization of the ads they see on the web. It's a one-step, persistent opt-out of personalized advertising and related data tracking performed by companies adopting the industry privacy standards for online advertising."
It is very similar to Google's IBA Opt-out extension, which allows you to permanently opt out of the DoubleClick cookie, which is an advertising cookie that Google uses.
This new extension works beyond DoubleClick and thus fears AdSense publishers and more, such as affiliates and other publishers who use other ad networks.
The thing is, you really don't have to worry. I bet you will not see any decline in AdSense or advertising income directly associated with this extension.
Only people like you and me will know enough to install it. It is only on Chrome right now, yes, Firefox and Internet Explorer will get it, but how many people will turn it on. Heck, I personally like my ads to be behaviorally targeted, so I am not running this extension.
Worried? Some others are also, but I really don't think you need to worry about this.