• Wikipedia is non-profit, but it's the #5 website in the world -- serving 470 million people every month with billions of page views.
• Wikipedia work hard to keep our operation lean. Google might have close to a million servers. Yahoo has something like 13,000 staff. Wikipedia have 679 servers and 95 staff.
• Wikipedia will never run ads. Commerce is fine. Advertising is not evil. But it doesn't belong in Wikipedia.
• If everyone reading this made a small donation, Wikipedia would only have to fundraise for a few hours. Not everyone can or will donate, but each year just enough people decide to give.
• Wikipedia only raise what Wikipedia need. When Wikipedia has raised Wikipedia budget, Wikipedia stop fundraising for the year.

http://en.wikipedia.org/wiki/Main_Page