I do agree on the fact that it is totally embarassing for Dropbox, and I do not either recall a similar issue with Microsoft, which does not make it safe. DEP / ASLR mechanism have been "easily" bypass several times this year, which to me is also embarassing. But the fact that this issue happened with Dropbox does not mean that it will again, and I'm pretty sure that it will make security one of their top priority. I do believe that going to Microsoft for better security is an odd move.