We think we've figure out Twitter's big news tomorrow: Oprah Winfrey is joining Twitter. Here's the evidence.

She's already set up an account. Ashton Kutcher, a big Twitter user, is scheduled to appear on the show Friday to talk about Twitter. Ex-dating columnist Julia Allison is trying to recruit other Twitterers for the show. And videoblogger Robert Scoble has posted that Oprah is going to be doing her first tweet.

With so many Internet celebrities on board, how can it not be happening?

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