As I recall, the first time I heard the term "gun show loophole" bandied about was after some of the Columbine shooters' weapons were found to have come from a gun show. What was conveniently ignored was that they were purchased at the gun show through an illegal straw purchaser and thus "closing the gun show loophole" would not have prevented them from acquiring the guns.
As has been mentioned, federal law applies whether one is buying a gun in a brick and mortar store, online, or at a gun show: any gun bought from an FFL holder is subject to a NICS check and guns bought from private individuals are not. When the anti's bemoan the gun show loophole, what they really mean is that they want their tentacles in private transactions. If anything can be accurately characterized as a "gun show loophole," it's the poorly-written law that fails to clearly define the difference between occasional private sales and engaging in the business of selling firearms.
Smith, and Wesson, and Me. -H. Callahan
Well waddaya know, one buwwet weft! -E. Fudd
All bad precedents begin as justifiable measures. -J. Caesar