Once you contact them they will say something along the lines of if you don't give them a piece of your adsense earnings then they will put invalid clicks on your site and then that will cause Adsense to cancel your adsense account. (Which by the way is very hard to get back once your adsense account is cancelled - especially for invalid clicks!)
I have been to a number of forum sites where people will ask - even beg - people to click on the ads to their adsense sites (so that they will earn more adsense money). I sometimes wonder if Adsense themself have seen these kind of forum sites where people are begging people to click on their adsense ads.
I do remember seeing where Adsense prohibits this kind of thing on sites that have Adsense ads on them but I don't think that they are aware of these forum sites where people are begging others to click on their adsense ads.
This adsense "pirate" thing was in the news a while back but recently others have been posting about it. For example someone reported that they got a comment on their blog where someone said that if they didn't want invalid clicks on their blog then they should contact them. Fortunately this person knew about the Adsense "pirate" thing and they simply ignored the comment. (Another good reason to have your blog comments moderated!).
Personally, I have a stats tracker on my sites and I have seen instances of invalid clicks on some of my sites and I have seen that Adsense simply discounts them as invalid BUT Adsense did NOT disable my account!
However, if you do get this kind of message then you should send it to Adsense as I am sure that they would be very interested in this kind of thing and the people who are sending you this kind of message!
