I discovered this article rather late, but the complete lack of criticism in the comments regarding missing user notifications in Dropbox amazes me.

I fail to see how silently creating conflict files and not letting the user know is better than notifying the user of conflicting changes.

You'll have to make the decision (to discard one of the files or somehow merge them) anyway.

Chances are, the user never notices this or only does much later, when there is already a mess of files of then-unclear content.