These days I ignore the ads, since I don't see why I should give money well as time: and they are obviously aimed at Wikipedia's readers, who outnumber the people seriously involved with the site by a factor of 10,000 or more by now.
I share the same feeling. As an editor, I think I contribute to Wikipedia sufficiently so as not to feel bad for not donating. The thing is that I would love to donate, but the endless heckling from deletionists have left a bad enough aftertaste that I won't donate anything more than my edits.