Do You Trust Wikis?

Today John McCain announced he has picked Alaska Gov. Sarah Palin as his running mate. In its morning broadcast, NPR reported that McCain's choice showed up on Wikipedia (and the AP) before it had been officially confirmed as fact.

This isn't exactly an irregular event in wiki world, considering the content is created by millions of users, but it says a great deal about the power of the Internet. In the hours following the official announcement, Wikipedia users frantically updated and edited Palin's entry, adding nasty descriptive words after her name (I took a screenshot of one, but it's honestly so lowbrow I don't want to share it).

I use wikis as one of my first stop spots to learn about people and random topics, but I can't say I take anything I read as verifiable fact. How and when do you trust wikis?