This has been discussed before as a bad idea. Unless Dropbox has improved, you'd likely run into syncing issues like I did 6 months ago.
On the other hand, the top voted answer on this SO question demonstrates how one might use a Dropbox directory as a git remote, so that you can push code there intermittently, preventing the trouble with constant writes to the Dropbox.
That's exactly what I do - "remote" repository in dropbox and push/pull in a "local" copy in my home folder. Works just fine for sharing code between my own PCs. I use it only for my personal projects, sharing repos this way is just asking for repo corruption -- if you both push at the same time, say goodbye to your repo.
On the other hand, the top voted answer on this SO question demonstrates how one might use a Dropbox directory as a git remote, so that you can push code there intermittently, preventing the trouble with constant writes to the Dropbox.
http://stackoverflow.com/questions/1960799/using-git-and-dro...