I gave a pretty significant donation (4 or 5 figures US$) a few years ago. In the letter I sent with my donation, I was very clear that:
1) the donation was anonymous, and
2) I did not want a lot of hard copy mail telling me about their work. that I'd prefer to get info about their work from their web site and that they save printing /mailing costs to use for their programs.

Despite that, they are still sending me thick mailings of info. I emailed, called, and sent the stuff back saying "refused" and "take off your mailing list" I still keep getting fairly expensive mailings from them, even though I only gave that one time.

I hope they did better on my request for anonymity but I don't trust them for honoring or respecting donor's requests.