Share picture.

I take a picture in a family party and I want to share it with my
family. I can simply send an e-mail to all my family contacts. Or I can
share with them by using their prefered method, and make it easier to
search the picture by submitter, tag, etc. And I want to allow them to
comment, etc. Damn! E-mail allows all of that, and has allowed for many
years.

OK. Subscriptions and channels are good features (mailing lists solve
that as well).

Where is it stored? Locally, on every subscriptors computer? Do
store-and-forward just like MTAs do? What does the network look like? Is
anybody going to keep their computers on, and share the load? What are
the guarantees? Use supernodes? Use tor or tor-like onion routing? Or
simply end-to-end encryption?