Ask HN: Multi-User/Platform Photo Management

I have an itch, maybe someone already scratched it :)

I'm looking for a photo management "thingie"[1]. What it should have would be multi-user support.

By multi-user I mean I save my stuff in the "thingie" and each and every one I approve has the same rights. I don't need or want a permission system, all I want is that when I save a photo someone else tags it. I see the result. No duplicated effort.

Does anybody know of a solution like this or did I at least infect some of you working on photo services with the idea?

[1]: I'm not quite sure I want to have that as a pure website or online service. Maybe some hybrid form where photos are stored locally and then (optionally?) backed up somewhere.