Since Overstock uses a payment processor to accept bitcoins, essentially removing any risk of loss, they are not being hit by this downtrend. Well, except for any holdings in BTC that they possess. However, that was not a requirement in order to be able to accept BTC.
There are probably a few merchants that were taking a wait-and-see approach to getting on board with accepting Bitcoin. When they see that it is possible to accept Bitcoin even through a halving of the currency's value without risk of loss, they may be willing to start accepting BTC. You can't really do that with US dollars or any fiat currency for that matter. If the Fed Reserve decides to double the Dollar money supply overnight, merchants would have to double their prices. Since the payment processor takes on the risk of sudden fluctuations instead of the merchant and calculates the amount of BTC needed, the merchant will weather these types of storms without having to concern themselves with BTC's changing value.
I think merchant adoption rates will depend on how Overstock does through this downtrend, and it appears they are doing just fine.
here's an even better ray of sunshine I'd say:
https://twitter.com/gavinandresen/status/434148075276206080
