Given that it costs less than $20 million to run Wikipedia (cite: http://upload.wikimedia.org/wikipedia/foundation/a/ac/FINAL_... ), that seems completely attainable without needing to change the nature of Wikipedia by introducing advertising. A lone rich donor could cover the budget for an entire year, and many people who could afford that wouldn't even be mentioned in Wikipedia, so there would be little opportunity…
And thats not mentioning the over 7 million (40%) on salaries and wages..... I'm not sure you can describe this as a 'small non-profit'....
Sorry if that all sounds cynical - but this is a not-for-profit institution here... I think that they have a duty to provide an efficient (value for money) service, which I am concerned is not being done....