I've always thought Google should just buy them. If you're going to index the worlds information, this is a good start. Google has the resources and power to make sure it remains alive and well.
Are you sure the owners would accept the offer? This allows Wikipedia to be truly free.
However, in reply to your question: In many (I'd argue most) cases, people have a price. Hell, I'd bet that with enough billions you could bribe a hell of a lot of married couples to split up, yet alone someone to abandon their community spirit and sell a volunteer-run organisation.
(Second paraphrase doesn't, however, top the first.)