While testing iOS 4.3 Beta 2, I came across a mysterious error message proclaiming PHOTOSTREAM_NO_NETWORK_WIFI. Thanks to 9to5 Mac digging into the iOS file system, that message makes some sense now: It may be referencing Apple's new media streaming service.
Apparently there are several more references to a "Photo Stream" and a "Media Stream" hidden within the iOS system files. There are alerts and graphics indicating privacy settings, subscription options, an invitation system, and a connection to Mobile Me. Based on those things, 9to5 has already dreamed up how a new service might work:
From the looks of different alerts and plists, it appears that Apple will let iPhone users set up "Photo Streams" that friends could "subscribe" to. Also, it looks like there will be some privacy preferences related to this, so you can choose who is allowed to view your "Streams."
With Photo Streams, you will also be allowed to "invite" other users to view your pictures as you take them and upload them to a service. This service looks like it is connected to MobileMe, and we speculate that "Media Stream" can be directly connected to "Find my Friends." We think Find my Friends will be another aspect of Apple's social network, a part of a free MobileMe, where you can choose to view your friends' "Photo Streams" all on that same map. Apple has a patent on something called iGroups relating to this. This would clearly tie into the Mac and iOS photo app's Places feature. From looking at the SDK, it looks like "Media Stream" could very well also have a plugin counterpart, like AirPlay, in 3rd party apps.
While all of this is speculation based on a few files, folders, and alerts, the details do sound fairly plausible. Of course, even if this service becomes reality, it may still be ages before we can actually use it. [9to5]