Actually, even very dumb algorithms totally destroy the problem you describe in your third paragraph.
Even if all you do is organize by date and show the first few photos for each day ("featured" photos), that's enough to vary the stream of photos people browse through.
I speak from experience, as someone who runs a photo-sharing site that organizes by date. I also make it easy to switch between featured/non-featured for any photo, but doing such switching is not a prerequisite. You already have a nicely varied collection just by uploading.
From what I've seen of Snapjoy so far, their format also guarantees variety. I haven't seen the fancy algorithms in action yet, but I imagine there are techniques one could use to make the initial set of "featured" photos more likely to be varied.
Even if all you do is organize by date and show the first few photos for each day ("featured" photos), that's enough to vary the stream of photos people browse through.
I speak from experience, as someone who runs a photo-sharing site that organizes by date. I also make it easy to switch between featured/non-featured for any photo, but doing such switching is not a prerequisite. You already have a nicely varied collection just by uploading.
From what I've seen of Snapjoy so far, their format also guarantees variety. I haven't seen the fancy algorithms in action yet, but I imagine there are techniques one could use to make the initial set of "featured" photos more likely to be varied.