No..No..i have never lost a single penny there..i am a having a seller account and its just like selling your very own material through them or you can even make someone else's material to sell and then gain commission from that..you always have to open an account by depositing some basic fee..in my case i've deposited 25$ and till now have made 170$+ sales..so, that got compensated in no time..this fee ensures that you are genuine enough in using their companies ads for your product advertising..commission fee they take is much less than google adwords..and moreover you are guaranteed of getting your products sold..