As I’ve noted, FoF apps turn out to be much less interesting than people thought at first. Do you really look at the photos of your FoFs? The main FoF app that seems to be useful is LinkedIn’s “search your network” which can answer questions like, “Who can I contact at Company X” and dating introductions. FoFoF turns out to be surprisingly non-useful.

However, I won’t proclaim that nobody can think of useful apps (or simply entertaining) apps here. So there need to be solutions, even if it turns out to be that those apps get access to large networks, but are the only ones that do. (Remember, our alternative today is zillions of apps getting access to this data.)

I don’t expect home PCs to be required here. Everybody wants an always on host for many functions. You don’t need it in the sense that I don’t think “Ask 100 hosts to search for a query” is a good implementation, but I would use the local hosts just as a way to do things efficiently for the user when the user is signed on. The cloud host would do things for others. Client data hosts and cloud data hosts would sync.

Your particular app, and other FoF apps, could be implemented, somewhat less efficiently, with data updates. That is to say, if you are using an FoF app, you would send changes to your friends, and they would forward those changes on to their friends as part of the update stream. In this case everybody is storing all the basic data (not big things like photos, just smaller stuff, including the URLs/access tokens of the photos) on their own host, and apps can operate on it. This is why it does not scale to FoFoF, but I think it could handle FoF if the updates are not large.

Of course, you, your Fs and your FoFs must be running the same application, but that is the same as saying they are all members of Flickr. To implement Flickr you need more though, and it may not even be possible to implement all apps in this manner. Still better than implementing them all in a central repository manner, though.