The problem I have with JPEG, other then the limited data it captures for a scene, is that every time you copy it, edit it, or save it the file is degraded and IQ suffers. If its a one time job then JPEG might make sense, but if you are trying to create an amazing image and hope to refer back to it many times over the years then your image will break down over time if JPEG. Also, as editing tech improves all that extra data in a DNG file can be exploited to improve your image.... DNG never degrades with copying, editing etc... It's timeless and a hedge that editing software in the future will be able draw more out of the data.
Hard drive space is so cheap these days that the filesize of RAW does not bother me one bit. Also, I cull images that I will never use or that were not as good as one that is similar or if it is OOF, etc...
The argument shooting JPEG over RAW due to Harddrive space is a silly one. Our camera kits contain thousands of dollars worth of camera bodies, lenses and accessories.... yet it's too expensive to go to costco or best buy and drop $120 on 2 Terabytes of storage!? Even CF and SD cards are relatively cheap especially when considering the old days of shooting film.
A funny story on that though. My mom switched to digital a few years back. Just point and shoot for fun. I found out that she had over 20 2GB SD cards and asked why she had so many. Her response.... because they kept filling up! LOVE IT!!! (Still cheaper then film....

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