Do Firefox Wiki :
- Sync currently does not support the following:
- Web access of your data - Since your data is encrypted on your computers, you cannot log on from any computer to access your data. You will need the Sync software to decrypt your data and display it to you.
- Home/Work Profile support - You will need to set up two separate Firefox Sync accounts.
- No Sync on quit - Your data will be synced when you restart your browser. You can also manually force a sync before you quit if you need immediate access to that data.
Portanto, pelo menos por enquanto, a resposta é "criar contas separadas ou usar Xmarks até que o Firefox Sync tenha mais recursos concluídos. ( é ainda em beta.