The card’s cooler is sitting at the back and you can’t really stack three or four of these cards next to each other because the cooling would have to suffer.
Practically, the card next to the first one would block the air intake for the other GTX 680 and thus really hurt the cooling efficiency of the cooler pictured here.
From my experience with building space-constrained systems holding multiple Tesla cards inside, you can only make them reliable if you build a custom shroud and, with the help of a high-power fan, force air into the space between the cards and thus make sure that the card’s fan has some cool air for intake.
Otherwise, you can always enjoy the fact that the card’s cooling system doesn’t render the PCI slot next to it unusable and install smaller cards like sound adapters, RAID controllers or network interface cards.
The 195W TDP of the GeForce GTX 680 is a lot to dissipate for a single slot cooler, so it is likely that the card might have working frequencies lower than Nvidia’s own reference card or they may be left at default specifications.
The device will be a good fit for smaller, mid-tower PC or any cramped systems that can’t really handle a reference GTX 680 or for cramped systems that still have two PCI-Express x16 slots and are able to run SLI, but don’t have room for two reference GTX 680 cards.
However, on the other hand, this could only be a show card and would never see series production.