Facebook founder Mark Zuckerberg, with longtime girlfriend Priscilla Chan and their new puppy Beast, finally announced on Facebook that he is "in a relationship."

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acebook founder Mark Zuckerberg updated his own Facebook page Sunday to indicate that he is "in a relationship with Priscilla Chan" — his girlfriend since 2003. The seemingly out-of-nowhere status update, which included the understated comment "Slightly overdue :)," comes not long after he and Chan, who share a home in Palo Alto, Calif., bought a dog together. Of course, the rumor mill has been set in motion — and the jokes are flowing. Here's a sampling:

Big move, Zuck
"Oooooo, how sweet," their relationship is finally "Facebook official," tweets Scott DeYager. "And to think, it all started with a poke."

Chan 1, Zuckerberg 0
All those years without adding Chan to his Facebook page? "The cheek," says CurrentTV. "I wonder how long his girlfriend had been nagging him."

Who can blame the guy?
"We get why it took so long," says Adrian Chen in Gawker. As soon as you change your relationship status, you're flooded with an "excruciating torrent of comments and 'likes,' from people you haven't talked to in years, all trying to outdo each other with the snide congratulations filled with gross innuendo." Congrats, Zuck!

Now they can never break up
"Let's just hope they stay together for a while longer so they don't have to go through with the embarrassing 'Mark Zuckerberg is single'" announcement, says Cress Ferriera in the Albany, N.Y., Times Union.

Protect yourself, buddy
Worth $13.5 billion, Zuckerberg is "the 52nd richest person in the world," says Daniel Bates in the Daily Mail. Is there a Facebook app for "a pre-nuptial agreement"?

He must have hit the wrong button
Yup, "Mark Zuckerberg finally changed his relationship status on Facebook," tweets Mandy Stadtmiller. "He went from 'single' to 'I could buy & sell every single one of you.'"