LB,Asus also released a 6800gt dual in August,but just like the 7800gt dual it wasn't mass produced(only 2000 made)
Asus use the cards more as a technology showcase,kinda showing off if you like,although Gigabyte were first
to release a SLI single pcb= 6600gt Dual
The dual chips also require Asus specific drivers[which prevent you from updating to the latest forcewares straight away]
Read performance analysis and conclusions on this page it states you need an ASUS nForce4 SLI chipset in order to run the cards!
My point is,your right,if in the market for 2x 7800gtx's no one in the right mind would buy one of these