Ads take up more space than the posts. I hate to think of the additional data charges and slower system response that go with advertising proliferation.
Suppose I'd feel less of a need to donate to the site since there is an ad revenue to support it.
Any app I purchase comes ad free. I really don't want to pay to receive more ad copy than useful post.
Maybe there is a way that donors could have the pop-ups blocked when they participate.