Hey! I'll personally pledge a couple Bitcoins

Nice idea Bruno!
Unfortunately I think the reasons charities dislike Bitcoin donation is that they think it's illegal/scammy and they don't want association with it.
Quick though!
For sake of argument, let's say Wikipedia is a new idea and Bitcoin has been around for a few years with a proven track record. Jimmy Wales would be knockin' on the proverbial Bitcoin door asking how to get one of those Bitcoin donation buttons on his Wikipedia site. He would be expressing to us how his idea will change the world on how knowledge will be shared globally. How his pet project is open source and run by volunteers, but desires donations for R&D, servers, etc. I sincerely doubt we would reply with a thanks, but no thanks, for considering Bitcoin.
That said, there's an election year coming up, and many small names on their respected ballots are strapped for cash. To us, it shouldn't matter what political spectrum they embrace. What matters is getting the Bitcoin name plastered (for sake of a better word) on as many sites as possible. Damn the chicken and egg dilemma. In due time, sooner than later, the technology will be forced to catch up with the demand.