Rather begging than pimping
My view is that I'd rather have Wikipedia seek donations (beg for money) than place paid advertisements - once advertisers start funding it, they'll be after editorial control either subtly or not so. While Wikipedia's veracity is sometimes questionable, I'd rather it was because of human error than down to the influence of the filthy lucre.
I just wish they could do it more subtly rather than the big yellow boxes and the 'sky is falling' messages which just turn people off.