In a rather extraordinary example of begging for money, Florence Devouard, Chairwoman of the Wikimedia foundation has told an audience at the Lift07 conference that Wikipedia has the financial resources to run its servers for another 3-4 months, and that without further funding Wikipedia “might disappear”.
As the article notes, Wikipedia is one of the most popular sites on the web, with tons of traffic. It's also influential, with users depending on it for all kinds of information.
And it appears to have no particular model for generating revenue. Culturally, this has got to be difficult for them: the usual approaches (advertising, subscriptions) are foreign to the Wikipedia DNA.
But a Wikipedia with ads on the page or a subscription fee for unlimited use is better than no Wikipedia at all.