Thank you for posting and sharing your thoughts. There would be much more behind the scenes work to do in order for a sync to work with Dropbox.
A simple file-based sync does not work properly for a Brain database for many reasons. For instance, many large files are modified in small but interdependent ways when the database is changed. Thus, a file-based sync is not only very inefficient, but also prone to corrupting the database. (When for example, the same database file is modified in two different places at once, a file-based sync will have no choice but to ignore one of those changes - likely corrupting the entire database!)
Additionally, there are factors beyond just the visible data that need to be kept in sync, such as index information, internal IDs that are different across machines, and so on.
This is why DropBox and other file-based sync services will work, but cannot be relied on since they tend to lead to corruption as soon as: 1) Changes are made to the data from more than one place at a time or 2) A sync is only partially completed before changes are made at the receiving computer. Worse yet, the database may only become partially corrupted so that you do not find out about the problem until weeks or months later when you cannot easily revert to a backup.
We recommend backing up your Brain on TheBrain Cloud. If syncing to TheBrain Cloud is not an option for you, a .brainzip backup is the next best thing. .BrainZip backups, however, need to be created manually.
Dropbox is a great service and they have managed to scale it to a huge number of users, however, syncing files and folders is far far simpler than syncing brains. A brain is a complex, interconnected network of nodes built on a database backend, it's not as simple as syncing individual files. The sync of brains is a highly specialized piece of engineering that we have literally been working on for over 10 years.