I maintain 2 PCs by using the Backup/Restore Library functions in RB6 and before in RB5. At home, my desktop drive containing the track and database files is shared on my network. I copy track files from the desktop manually to the laptop, my performance PC. Guess you could accomplish this automatically by using Dropbox or Google Drive.
I then Backup the Library database on the desktop and Restore it to the laptop. This syncs all my playlists and cues on both systems. I reverse the process by Restoring from my laptop to sync any changes made during gigs. This also creates a backup of my database in case of a major failure.
I believe you are thinking that if you have Dropbox or Google Drive, this process would be more automated. Changes to one system or the other would be pushed to the cloud service and then pulled to the other automatically. I wonder how timing would effect the synchronization process.