Just a few quick examples:
1. There's HAWK and OAuth2 and BrowserID there, all in the same system. That's a lot of undesirable extra complexity.
2. The Sync 1.5 protocol itself is full of non-standard weirdness, with odd stuff like X-Last-Modified (which is just like Last-Modified but with UNIX timestamp - seriously?). While I haven't experimented writing an adapter yet, I strongly suspect a plain old' WebDAV (with a tiny little bit of sub-standard collection stuff) would've worked just fine and even better.
3. Poor documentation. The documentation was draft quality when Accounts and Sync were just rolled out (so it required some reverse engineering), but that's understandable. Things have improved since then but I believe a lot of stuff isn't really fully documented even today. For example, some undocumented magic is required to show Accounts sign-in page on iOS.
My point is, the whole thing is absolutely not developer-friendly (unless you're a Mozilla developer), as it makes self-hosting and alternate implementations quite difficult.
Maybe my problem is Accounts and Sync is not a standard (neither a proposal to become one), but just a documented vendor-unique API.
Openness is in the same boah as privacy. Average user would buy just a "we pinky swear it respect your privacy" sticker on the product, but we know they want real privacy. Same with openness. And Firefox Account & friends is not an open system, it just happens to be partially documented and have a few FLOSS implementations of varying quality.
Kinto is a step in the right direction, though.
> One could, however, add a second passphrase that is never sent to the server, and encrypt the data using that. Chrome provides this as a non-default option.
The average user doesn't have the expertise to know that they have to configure an additional "master password" to keep Google from mining their data for ads.
https://prod-cdn.sumo.mozilla.net/uploads/gallery/images/201...
I just got this morbid idea of Google mining storing passwords to recommend LastPass/1Password in ads based on your password strength.
The advantage here is twofold. - Your encryption key is derived from your single Firefox password, rather than having 2 passwords. - The ease of use of this system makes it possible to have e2e encryption by default rather than by opt-in.