I think this site would be very useful in the classroom. We could create montages of fieldtrips, and if the text did not cost money to add, or if I invested, the students could use it to recount the events of our trip. Hopefully focusing on what was learned, and not just the social side of an outing, though that may have a place in building a classroom community that we can share beyond the walls of said classroom. Hmm, that is more photo food for thought.
I imagine this site could be used across the grades as well--I would have easily used it when I taught Kindergarten to record activities such as show and share, using building blocks, baking, book making, finger-painting, puzzle making, just about anything. In middle years I would have used it to record volunteer endeavours such as working for the food bank, cleaning a green space, visiting a nursing home.
What I think would be really interesting, would be to ask the students how it would be best used in the classroom. Especially for those of us who have worked or are working in school divisions that restrict access to such sites. Having students debate the educational virtues of such sites and writing persuasive letters to the administration and school board might be a very useful activity indeed!