Technically it should be possible to fetch the page and parse the title tag. It's hard to know when to do that if there's an editable URL field. With a browser extension and a "?add=URL" parameter (see the question from g4k) it would work better.
I'm not familiar with remoteStorage.js. Dropbox I chose simply because it's popular, many people already have an account and trust them, so it's a low barrier to use something that uses Dropbox.
The library primarily supports 'remoteStorage' providers but apparently now supports google drive and dropbox experimentally.[1]
All the apps using remoteStorage that I've checked out don't seem to have dropbox as an option though, and only some have google drive.
[1] https://unhosted.org/adventures/7/Adding-remote-storage-to-u...
I wish it would auto-determine bookmark titles. Unless that is a Safari-only issue, I guess that is due to its client-side nature?
Also: Why not remoteStorage.js ? Not that I particularly care for that over dropbox.