Profile: Randi Zuckerberg, social networker

The surname rings a bell...

That's because this is the big sister of Facebook founder Mark Zuckerberg. For six years she's been his right-hand woman, responsible for some of the social network's most successful innovations. But now, in a move that could take sibling rivalry to a whole new level, she's announced she's leaving Facebook to set up her own media empire.

Brothers and sisters, they just can't share. Will Mark be de-friending her on Facebook?

Well, it's not yet known if they had a falling out. Mark Zuckerberg hasn't made a comment. In her resignation letter, Randi Zuckerberg said she had "poured her heart and soul" into Facebook, but was now after "other ways" to "affect change" as "now is the perfect time for me to move outside of Facebook".

So what's her new company called?

It's a cheeky pun on her name; RtoZ Media. Its goal is to make media companies "more social" (she's got Facebook in her blood after all). She'll be drawing on contacts made while at Facebook with TV networks and news agencies, helping them spread the word through different media in different ways – just like she did in 2010 when Facebook teamed up with the ABC network to cover the US congressional elections. She was nominated for an Emmy for her efforts then and will have high hopes of breaking new ground in the business world now.

This sounds like it's got megabucks written all over it...

Maybe. She's got a long way to go to before she can rival Facebook, which could be worth $100bn (£60bn) by next year, according to market projections. But Mark will be watching his back now there's another Zuckerberg on the block.