While using git and dropbox might appear to work most of the time, and shouldn't lose data, it's not an ideal pairing -- have a look at my answer to this stack overflow question: http://stackoverflow.com/questions/2199637/is-this-plain-stu...

TL;DR: Git's hashing means that everything's going to be there, packing means that it's going to be a very inefficient sync (and you'll wind up with multiple copies of the same data) and branches may not behave as you'd expect.