Here's someones take on it...I tend to agree, it's a mess...
What a pretty mess. And not as "clear cut" as the blog linked would make it seem.
NBC is claiming that the vast majority of the images were submitted to them by the subjects (with proof to back it up supposedly) and that the images are "joint works."
The claim that the images are co-owned by the subjects is not without merit... the reason for the photographs in the first place is the costumes, and the subjects spent considerable time/effort/money in creating them. In fact, it could be argued that the costume itself is an "original artwork;" that the photograph is a "derivative work" and therefore the copyright to it is "owned" by the costume creator.
The second question becomes "how did the subjects come into possession of the photos in order to submit them?" If the photographer provided the pictures without anything in writing it could be problematic. First, it would support the argument above. It could also be argued that providing the images without a statement of use constitutes unlimited use. And just because there were no rights granted in writing does NOT necessarily mean no rights were granted "legally." There is such a thing as "implied rights."
And then there's the Facebook TOS which says you sign away all rights when posting stuff there, that you will be governed by CA law, and that you waive the CA law protecting you from signing away your rights when it's not to your benefit... If the images were lifted from there it could add another wrinkle. Facebook strips all exif...oops. And publishing (text so far) to facebook/twitter/et all has been determined to be "publishing to the public domain" where no copyright is possible. It's not a big leap to see this going sideways.
Because it's NBC, there's potential that many are going to want to "cash in." I'm sure a lot of these photographers were just "taking pictures" and posting/distributing their stuff without restriction and now they want to "change their minds." If it gets costly enough NBC could choose to fight it, and they could win at least some (or not loose nearly as much). In the end, I hope NBC is found to be at fault, as well as the subjects who submitted the images as being "theirs." But I wouldn't count on it.
This is a convoluted mess because a lot of people did not know WTF they were doing...