The Digital Negative format (DNG) was created to offer an alternative to the proliferation of different proprietary RAW file formats to help ensure the survival of images created, when such formats become obsolescent. (so long as the image file has been converted to DNG)
DNG has a number of advantages:
1. Its not proprietary in the way that the camera manufactures RAW formats are, so it can contain the image modifications within the file not in 'sidecar' files, thereby reducing the number of files one needs to keep track of.
2. A DNG RAW file tends to be smaller than the Manufacturers RAW file and still contain all the image data. I have found a saving in file size of approx. 11% when using DNG rather than Canon (.crw) and Hasselblad (.fff) although the lens and moiré corrections are still reversible using Phocus* with .fff archived files whereas they are fixed in DNG at time of conversion from .fff
3. From a Photo-Archivists perspective in addition to the above reductions in number of files and size we now have a format that can survive the demise of proprietary system manufacturers, and planned/unplanned obsolescence.
* Phocus is Hasselblads latest Raw Conversion software that is integrated with Lens and Sensor design.
On Line Learning
You can download 'Adobe Creative Suite Video Podcasts' for FREE via the iTunes Store, there's an excellent one on the subject by Terry White entitled "Why DNG"
Adobe DNG Converter Download
Apple : Download
Windows : Download
Digital Image Preservation
Through Open Documentation
"The RAW Flaw"
by Michael Reichmann and Juergen Specht
by Stuart Nixon