I was not the only one who witnessed this. Here is a report from someone helping out with conference activities, "You should've seen librarians taking free books for autographs and then ducking out getting in another line and going again without ever going through the line for the autograph."
And this from someone in publishing, "It's like this at all educational conferences and disconcerting, indeed. Always hopeful the ARCs will be read and shared."
And this from another librarian, " I get SO mad when people just swoop and grab. They don't even look to see if it would be fit for their campus."
There were others who affirmed what I saw, but I have seen it at many conferences as well. It is inappropriate behavior. There is no excuse, either. If you want multiple copies, ask. If you are looking for some swag to give to your book groups, ask. If you want to hand an ARC to a colleague, ask.
Quit making excuses for behaviors you would correct in others.