They needed to do a "study" to figure that out? It's common sence. What's next, a study to determine that milk goes bad if you leave it out in the sun?
I've sold 2 guns in my life at Saxet Gun Show. One was a .380, and when I asked the guy for his license so I could take his info down, he showed his CHL, so there was no point. The other one was to a guy with a stand and an FFL. I'd have to guess that the majority of people who sell privately don't want to sell their guns to some BG, only to have it come up in a crime, or even a murder. I know I wouldn't want it on my concience (sp?), let alone have police coming to my door asking questions.