One of the arguments against bitcoin is that it is deflationary (ultimately) so people will spend their fiat before they spend their bitcoins.
So the desire of people to keep bitcoins (and spend USD because it's less valuable) is a reason for their unwillingness to buy bitcoins. I see some logical contradiction here. Either people don't want bitcoins because they don't understand them, don't trust, cannot buy and spend them. Or they want to buy bitcoins for whatever reason - to invest or to spend elsewhere. But you cannot say that willingness to keep and not to sell BTC is an argument for not buying it.
lets just say all the traders on gox based their pricing thoughts on memory dealers, alpacasocks and SR for instance.
instead of those three selling an item worth $21 for 1BTC. you want them to sell it for 0.8BTC because the price in the future "should" "in theory" rise with time and the merchant would eventually break even by hoarding the coin.
my answer to that is: chicken or the egg
why: because although it may drive up speculation because now gox will say everyone is willing to spend more then $26 for a bitcoin (price of a whole BTC based on the $21 for 0.8BTC). they are only willing to do this because of speculation.
its fuelling itself with no bases in reality for the valued cause.
its better to stick to a proper value base, such as electricity costs+time+equipment costs+ small profit. and let the difficulty of the network drive the price for ACTUAL value/cost.
my second answer is: merchants need their fiat that week to buy more stock. so basing it on a projected value of 6 months time would lose him money when he cashes out at the end if the week.
the only way it would work is if middle men gave the merchant his £21 for his 0.8BTC that week and they hoard the coins for the speculated rise it causes