That story makes me want to become a goat farmer every time I read it, but, Dropbox must have intended that usage if they had a publicly available API, right?
According to TFA in parent Dropbox happily had them on a custom plan, charging them more and more as their data grew.
Dropbox as a VCS for separate documents intended to be accessed by non-technical users is not a terrible solution. Certainly there are better options, but I think something built on Dropbox could be workable in this case.
Why use Dropbox if you could just use FTP + SVN/CVS? [1]