One of the common use-cases that pops into my head is as an equivalent for Flickr except massively de-centralized.
There are obviously many dis-advantages to using a non-centralized system, largest in my mind is the loss of the community feel, but for some people the fact that you are 100% in control of how your information is dealt with might be enough to win them over.
It's likely too that other developers will think of new and exciting things to do that will be unique to the platform, one killer app could make Unite really shine.
That's the biggest feature that pushed flickr to the top of the photo sharing heap. Which is why this is a losing proposition for just about every existing-app-killer idea. Maybe it'll provide a dead simple way to do something new, but any system that relies on consistency and availability (most social networking apps) will suck.
How many 404's before you delete the bookmark and stop coming back?
There are obviously many dis-advantages to using a non-centralized system, largest in my mind is the loss of the community feel, but for some people the fact that you are 100% in control of how your information is dealt with might be enough to win them over.
It's likely too that other developers will think of new and exciting things to do that will be unique to the platform, one killer app could make Unite really shine.