Robin2:
But does the Arduino team publish audited accounts so you can see what happened to your donation?
I remember reading a comment from Massimo Banzi that they were thinking of adding a feature where you could chose where your money should be spent when you donate or buy a board (I can't remember which but I think it's the former). I think that would be great because I don't want to support, for example, work on the closed source Arduino Web Editor (which is where a lot of Arduino's resources have been going for the last couple years). This is why I'd prefer to contribute my time to the project instead of money, because then I know exactly where it's going. However, not everyone has time to spare or the skills to make a contribution and money is important too so it's great to have the option of donating.