What's actually going on here? What sort of false positives might we expect from such a program?
It's not a stretch of the imagination that dropbox could still be making a profit spending bandwidth and storage space this way. I can think of a government agency or two that would re-imburse the costs.
I agree with what another commented brought up - it's probably just unfortunately overaggressive 'filesystem-watch' code - IE when you change a file it checks to see if it needs to be synced and re-uploaded. It shouldn't be able to affect other files, though. Makes me wish we had more nuanced security controls, like per-app permissions a la Android/IOS.