hi my friends ... i dont know if you all familiar with that .. but adsense give you the ability to make a list of the sites you agree that you earn adsense at .. and why is that important so people cant steal your adsense and abuse it and that might ban you at adsense .. anyway if you didn't understand me read from here this is taken from google adsense help .. i hope it help you guys What is my Allowed Sites list? Allowed sites are sites or URLs on which AdSense publishers allow or wish to have their Google ads displayed. If a URL displaying your AdSense ad code is not on your Allowed Sites list, ads will still be displayed, but impressions and clicks won't be recorded, advertisers won't be charged, and you won't receive any earnings for that URL. We've added the Allowed Sites feature because we've learned that some AdSense publishers are concerned about potentially malicious behavior from others on the web, such as stealing their ad code and placing it on an inappropriate site. By offering this feature, we allow AdSense publishers more control over which sites or URLs can have their AdSense code.
This is a good idea. because someone might use your adsense code and use it in their site and make you get banned.
and it keeps unethical persons from slapping the code anywhere 'they' wish. It's to your benefit since you're an ethical person.