There's the obvious reason of course -- fans of the first game really, really wanted a sequel -- but in an interview with Games Industry International, DICE GM Karl Magnus Troedsson explained some of the reasoning behind creating a sequel to Mirror's Edge, and game that, to an extent, was a bit of a commercial failure.
"We take a look at it from a gamer perspective," he explained. "Is this something we want to play ourselves? Do we believe in it? What does the heart say? What does the gut say? And then we take the business approach and look at it with the mind as well.
"But somewhere between the heart decision and the brain decision, you just need to make up your mind. Mirror's Edge is definitely one of those products. We're so passionate about this product; it's a game that needs to be built, basically. Is there an element of a leap of faith here, no pun intended? Yes, there probably is, as there is with all games as they're being built. You don't know if they're going to be a smash hit from the beginning. But do we feel like we're swimming out into an unknown ocean? Absolutely not."
I'm curious to see how Mirror's Edge goes. It's one of those games with a massive cult following in forums and Kotaku and the like, but is that audience big enough to justify the costs of a large scale AAA production? Will it end up being a vanity project? I suspect the game will be a success on a far grander scale than its predecessor, mostly through word of mouth, and perhaps through marketing lessons learned in the failure of the first game. Regardless, as a fan, I'm glad the game is being made. I think too many people have the nostalgia blinkers on with the first Mirror's Edge. It was far from a perfect game but it was unique and it was beautiful. It harks back to a time when EA was a little riskier with it's big projects. As a fan, I hope it's successful.
EA DICE: "You could market research any product to death" [Games Industry International]