Good questions. The answer is I don't know. I thought I would just throw it out there. It is basically Wordpress with a really good photo album manager and editor (like on G+). There would be a local store for data (album names, comments, posts) and all of the photo and video data would be held on my own S3 instance. Some kind of backup system to backup the database would be required incase my cheap shared hosting front end went tits up would be required (or I wanted to migrate somewhere else), but the base media data would stay in the same place (Cloud files / S3 / etc).

Yes, I'd be trusting Amazon or similar to securely store my media data, but I can live with that. It would be even more awesome if I could somehow encrypt that media data at rest. However, I'm not trusting a cheap shared hosting provider to look after my media, which is some where I just don't want to go with my multiple TB of media data.

How do I find my friend? Good question. How do you find your friend's email addresses? I'm thinking of a system where you authorize an email address to access your cloud. Your friend can then simply login with an email address link which issues an auth cookie for that session. No passwords and confusion about who is logging in where. Users can link their own clouds once logged in. The backend then uses some kind of OAuth flow to enable access between one cloud and another.

I'm splurging ideas here. I haven't really put much thought into them being valid or not btw!