It's not a loophole. You don't need a gun show for a private purchase, it's your right as an individual and you can do it anywhere. That said, most gun shows today are cognizant of the media frenzy over their labeled "loophole" so the promoters no longer allow tables to be rented to private collectors. That means most transaction on the floor of the show will go through an FFL and background check.
Certainly there may be folks walking through the show with a weapon for sale privately, but let's face it, it's not easy for a private individual to carry too many.
I would also like to comment that as Americans, it is our duty to make sure we don't sell to someone who has nefarious tendencies. As an FFL, I am happy to log and transfer a weapon for a private sale. It literally takes minutes for the background check. If I was a private seller, I would gladly pay the transfer fee to know there was a paper trail, for my own liability.