It's a shame that we need to fill in so many details just to donate a few bucks.
This indicates further that Wikipedia simply doesn't understand Bitcoin.
While you do not need to reveal yourself as part of the Bitcoin protocol they may need your personal information for some kind of compliance purpose (to comply with some law or regulation). I am not 100% sure what kind of "chairity" wikipedia is (what part of the tax code they fall under) however if donations are tax deductible they will need your information so they can give you a tax form so you can receive a tax deduction for your donation