See also: Brands that don't develop on android are missing out.
But it's not just about building cool apps. Traditional advertising is finding it's home in the world of Mobile. Apple is launching it's iAd platform which promises to "finally open up the advertising potential of mobile devices". Worth keeping an eye on this one.
Slight tangent - but there are more mobile phones than PC's - FACT. It's a great place to advertise, why? Because what do you never leave behind - your mobile phone. You might have a tablet like iPad or Galaxy, you might have an Air or similar - but the device you always have is your mobile. More and more we're moving away from the need to have a laptop/PC at least in the home. There is so much you can do now thanks to apps.
Few new features that will shake things up a bit / make mobiles more useful.
Google docs comes to iOS and Android (who needs a PC anyway?)
Mobile phones replacing your wallet? Yes - Nokia to enable contactless payment.