People get annoyed at them for their massive banners begging for money making it seem like wikipedia is on the verge of being closed down unless you donate despite the fact they have a ton of money they have saved away which could keep wikipedia running for decades. Even long running wiki editors and donators get pissed off with the behavior of the wikimedia foundation as not enough of this money actually seems to get spent on Wikipedia. Kinda similar to the whole Firefox situation now I come to think about it.