I also don't like that a relatively small mistake/bug can cause that my files can be accessed by some other user.
Good luck.
As Eric mentioned, we have an email to Dropbox to see if we can permanently delete through the API. Until then, we will have to rely on keeping the login information to these accounts safe, which is saved in the same high level of encryption as our user account information.
I am not sure that I follow how a small bug could cause your files to be accessed. All access to the user accounts are kept completely separate. We take all concerns with user data and security very seriously.
I guess I have to say that we spend a ton of effort minimizing risk and keeping security up, but you knew that :)
2. Privacy implications of intermediate step to your dropbox account seem to be pretty staggering.
3. Possible to get DDOS'd by monster files?