The question to ask is: "Do you need Wikipedia?" If Wikipedia charged a small fee for use of its site, would you pay?
You may use Wikipedia a lot. In fact, instead of the thermometer image (likely because they don't want you to see how ridiculous the amount of money they're making is), they've now chosen to use banners with quotes from donors. Check this one out: "As a professional scientist, Wikipedia is my go-to source for ideas and concepts new to me. Donate for this? You bet!" I am officially scared.