Nvidia have more partners selling cards than AMD currently has, as for selling directly, it's only with bestbuy in the states, no big deal. Don't forget it is Nvidia that gave XFX the bullet.
Bestbuy is BY FAR the biggest retail outfit in the states, likewise, its not only Bestbuy, its only Bestbuy in retail, its also only Newegg in e-tailers, again by far the biggest in the states. The biggest presence apparently in Bestbuy, was BFG, and Nvidia have like never before, demanded entire marketing strategys from all partners in the past year before making this move.
Retail sales are rather pathetic in the UK, in many many area's, from PC games, to PC hardware, not many people by invidual components in a store instead of online, the states still has decent sales in places like Bestbuy. For instance on OCUK I've pretty much never seen someone say "I bought a 5850 from purple shirt brigade, it sucks/rocks/blows/doens't work" etc, on US forums you constantly see people say they just picked up their card from Bestbuy, or hard drive, loads of overclockers go instore to buy a CPU because they can see batch dates/production numbers.
Bestbuy is in no way insignificant like purple shirt guys are here.
Nvidia have more than enough partners and EVGA eclipse XFX in terms of brand appeal. XFX asked for it really, going with AMD and opting not to sell the GF100, this was always on the cards, no great loss to Nvidia.
XFX asked for it? XFX were likely close to going under, they didn't go AMD 3 months ago, they went AMD when Nvidia had EOL'd the 285-260gtx, when Fermi was 6 months away and XFX had nothing to lose.
XFX also most certainly didn't opt to not sell the GF100, Nvidia, 6 months after XFX went AMD to save the business, wasn't given any GF100's to sell.
XFX asking for it? XFX likely would have been under without going AMD and I'm fairly sure XFX is exstatic it can sell a high profit entire like without prejudice from AMD and not particularly said it can't sell an Nvidia range with little profit, thats late, that won't be updated till probably late next year, IF Nvidia are on time.
Really it hasn't worked out badly for either company, just BFG. Nvidia could do with the extra margins from card sales rather than just GPU's, and the other partners, with XFX/BFG gone probably aren't losing too much in the way of sales.