I really wish it shouldn't have existed, and instead Mozilla would've focused on providing an API to build a synchronization service upon. And then, whatever - their services could've been an pre-bundled extension.
2. I believe all of those SaaSes (i.e. Firefox Screenshots, too) shouldn't belong to the browser's core. Those could be distributed as pre-bundled extensions (which they actually are, but in a special way), but not as a part of the browser itself.
This is highly opinionated, though. I just feel that rather than a browser, Firefox is becoming something like a service platform. I don't like it for the same reasons I tend to value self-hosting over the dependence on others' services, and Free Software over non-free options. I recognize others may feel very differently and possibly even welcome that.
---
[1] Authentication pages are still served from network, so if you use it - you trust Mozilla to not steal (or, better say, not be forced to steal) your password and the encryption keys. The protocol is stable for quite a while so I really don't know why they're still not fixing this.
[2] I wrote an alternative self-hosted Accounts & Sync implementation, so while I'm biased I sort of know what I'm talking about here. Four different authentication protocols (BrowserID, Hawk, OAuth2 and JWT), multiple non-standard HTTP headers, and the whole system just reeks of the NIH syndrome.