It can certainly be an uphill battle, with a user base that pales in comparison to the iOSes ad Androids of the world -- and then there's the fact that the OS hasn't actually launched in the States yet.
But a little scratching on the gold-plate of this ideal reveals it for what it is: a modern targeting technique, albeit a big step up from zip-codes, but certainly neither an answer to what consumers expect of brands in the digital space nor a guarantee of increased attention or ad contagion of the desired viral variety.