Upload & Sell: Off
Now that I've put the D800 through several thousand shots not just on tests, but on actual paying jobs, here is my conclusion: a 12-bit lossy NEF will produce just as good of an image as a 14-bit lossless NEF for my style of shooting. I don't shoot landscapes (I do weddings and portraits full time), I rarely do any sort of HDR processing, and I tend not to go nuts with filters and adjustment layers. If I have to rescue detail more than 2 stops under or 1 stop over, I'm not doing my job correctly. A 30MB NEF will produce essentially the same image quality as a 45MB NEF, for the way I shoot and the images I deliver to clients.
This has been the same conclusion from similar testing done with my D3S and D700, and to a lesser degree the D300 (one of my backup cameras). Along the way, I've been impressed by how well the D700 performs in low light, how the D3S is even better, and how the D800 manages to squeeze 36 million pixels onto the sensor without really compromising other aspects of image quality.
Thus, from an efficiency standpoint, I should be shooting 12-bit lossy NEFs. There is no perceivable loss of image quality, but there is a significant savings in terms of storage and data transmission times.
OTOH, storage isn't a big issue for me either. I went from 4GB cards in the D700 to 16GB cards in the D800. That more than makes up for the file size difference. I can shoot 14-bit lossless NEFs on the D800 and fit around the same number of images per card as I did on the D700 with 12-bit lossy NEFs. That means I don't need to keep track of more cards, or change cards more frequently during the day.
I also upgraded from a USB 2.0 card reader with SanDisk Extreme III cards to a USB 3.0 card reader with Lexar 400X cards. The former gave me about 20 MB/s throughput. The latter now gives me 80 MB/s throughput. Again, that makes up for the larger D800 file sizes.
Hard drives are still very cheap when it comes to bulk storage. I don't need fast hard drives for backup purposes, so a 2 TB drive costs less than $150. I can store 40,000 14-bit lossless NEFs or 60,000 12-bit lossless NEFs. If I deliver an average of 750 shots per wedding, I can store between 50 and 80 weddings on a drive. That works out to $3/wedding for 14-bit lossless, and $1.88 for 12-bit lossy. So long-term storage costs don't add up to much either.
I also backup finished weddings to Blu-ray, which then go off-site into a bank vault. This is where it gets a bit more interesting. Assuming a 750-shot average, shooting at 14-bit lossless will result in a data size of 33 GB. That's too big to fit on a single-layer 25GB BD. I'd either have to buy much more expensive dual-layer 50GB BD, or spend the time and hassle babysitting the burning of two discs. With 12-bit lossy, 750 files add up to 22 GB. That conveniently fits on a single disc, which means I can fire 'n forget the backup process. The entire wedding stays together, I don't have to keep track of multiple discs, etc. So in my case, the difference in NEF compression just happens to cross over that one-disc threshold in my backup process.
But for everything else, it really would not matter what mode I choose. It will not have a dramatic impact either way. Now, the debate between lossy and lossless DNG is interesting for other reasons... but I'll save that for another thread.