Easy there! MySQL is something completely different. If relational database replication would be as easy as Dropbox, then they would all support it out of the box. Do NOT use MySQL on Dropbox!

Dropbox is for stuff, which needs to be synced but is (usually) not accessed concurrently. The programmer with the Dropbox-git will not code on two computers at once.

No it's not. Git stores all it's internal data as hashes, and the chance of a collision is really small.

It was designed so it could be accessed via ssh for instance with multiple people pushing into at the same time.