Facebook almost bought Twitter for $500 million last year. The deal didn't happen — but the service found a fan in 24-year-old Facebook CEO Mark Zuckerberg. This morning, he revealed himself as "finkd" on Twitter.

Zuckerberg has had a private account under the username "zuck" for awhile. But Zuckerberg's confession to operating the public "finkd" accountcomes after VentureBeat reported its existence and wondered if it was a hoax.

It's not a hoax. An update "finkd" posted at 9:38 p.m. on March 4 ("A good day") matches exactly a status update Zuckerberg made to his Facebook status two minutes later.

Facebook spokeswoman Brandee Barker welcomed Zuckerberg to Twitter. And one of his friends is Christopher Cox, a close Zuckerberg confidante who's little-known outside the company.

So what does it mean that Zuckerberg has a public Twitter account on which he can overshare his thoughts with the entire Twitterverse, when he's made so much of Facebook's privacy features which let people share updates with just their friends? It suggests that Twitter's rapid (if utterly profitless) expansion is unnerving him — and he still desperately wants to bring the microblogging site under his wing.