One thing to be aware of with Dropbox is if two people have the file open and make changes DB will not save the changes both make to the same file. It is aware that two people have the same file open so it will ask you if you want to save your changes, then it makes a copy of the file with your changes only and gives it a unique name, something like "(your file name) Original" and dates it.
The other person's changes get saved to a separate file. I'm not sure if it saves the other's changes to the original or if renames it also, all I know is it doesn't save both changes to the same file. I was testing it for a customer and found it wouldn't work out for multiple users because of that, unless they were just doing read only.
The same would hold true for example if you had a file open at work, didn't close or save, and came home and opened the same file.