A ton of theories being presented via journalists and bloggers. Personally I do not know much more then the rest of them, but here is my 2 cents, and why I am excited about it:
1. Apple purchased a small map player a few years back.
2. Apple purchased Lulu.com (cloud based music) a few years back.
3. A patent was revealed a few days ago highlighting small storage of a song (or any other data type) locally, to start the application, then retrieve the rest from the cloud. Creating a 'real-time' access effect, and potentially unlimited storage capability.
3. Apple has iAds
4. iTunes platform as a distribution mechanism, and payment system.
5. We know Apple has been keeping track of the wifi locations users hit to build up their map system. (Info revealed during the congressional hearing about privacy and mobile phone tracking.)
When I look at this list, I see some very interesting individual applications, but when combined and glued together by a secure cloud, OMG, it can be an awesome opportunity.
1. Mapping with iAds, can produce location based Ads. Maybe partnering with a Groupon or LivingSocial to offer their inventory. Or maybe the iAds devision is already working on their own deals service. (I do think the 'deal offering' is going to be the primary means of local advertising in the future.)
2. iTunes in the cloud can facilitate a payment platform potentially incorporating #1. (Square is doing it via their Register, but this would be less cumbersome. Although, I also think Apple may acquire Square soon. They are in bed together too many times.)
3. The obvious chatter about file sharing, except with the patent, users can see potentially very quick real-time usage.
If certain services are done right, like being able to use Facebook connections, for #1, this could be a significant growth area for Apple. This is obviously not factored into the stock, not by any means.