There was a good chunk of time where I was converting all my Canon Raw files into DNG files on the thought that it would be better and make them more readable in the future. But with KDE able to read Canon files as well as the libRaw in Linux - it seemed a waste of time.
This article by a professional photographer gives another reason. Certain software may not be able to produce as good a result from DNG as when the files come unadulterated from the camera.