That's my top pet peeve. Pay and still see ads? Removes a major incentive. I rememer long ago RealAudio introduced a constantly-rotating ad in their player. Paid for it -the ads remained! Had to ask for my money back, deinstall, never used it again.
So, there's a reason for it. Namely, the way to implement that would require setting a cookie to say you've donated. And it'd be a cross-site cookie (because the payment is done on the Foundation site, not on Wikipedia).
The Privacy Policy is pretty strong on things like that: we don't set cookies unless there's a need to. Fortunately, you just click the 'X' button in the top-right hand corner and the banner will go away for the rest of the fundraiser... whether you've donated or not.
Can the donations be tied to a user account? What prevents checking 'user donated within 6 months'? (Assuming people can and do provide the information and remain logged in)
