I don't see it either (and I haven't been seeing any ads anymore for quite a while (if they are still supposed to be there?))
The ads disappeared some time ago as they reckoned people weren't really viewing them but just clicking on them loads of times so that the number of views registered was high..
In my view it was their own fault for showing nothing but dating sites; what good are they to bald-headed old anoraks like me?
I still have the 'Donate' button in the right place; perhaps those who don't see it don't need their consciences pricking?!