Great concept.. but the fatal flaw is using social media accounts as keys. Moz Sync..? Onedrive/Live, GDrive, other storage point like FTP/HTTP file, webdav, smb/cifs, discrete file, and object attachable or beamable. Hope it makes it.
I'm not shure that I can use MosSync in Chrome too. My addon also avaliable there. But I'm going to add different types of authentification later. And sosial media accounts as keys is the main feature that you don't understand.
