Pit fall in adsenseI have seen lot of people eager to make money and sign up for the google adsense. And they use the same account for various sites and even they use to combine with this site too. What happens they do self clickings and mutual clicks. GOOGLE will block entire things. so use single account for single site. especially use a seperate account for adsense sharing. They won't get you any invalid click. Very safe.
Moral : Use seperate google adsense account for seperate web sites.