more interesting is the coinbase lack of coins - this possibly tells us the miners who they buy from are now close to or below cost of production and are no longer selling OTC, forcing coinbase back to exchange and needing to move fiat back to bitstamp or others. This is more indicative of a floor than any large wall on stamp.
Don't expect a stellar rise though - once the price rises enough the miners will be back to dump their coins.
Most likely CoinBase keeps X amount of dollars on BitStamp and Y amount of bitcoins. They can reload as one or the other starts to go down which allows for the instant purchase when someone buys on their site.
But, there were so many people buying against that $300 wall that their X amount of dollars dried up...so now they need to wire more dollars to BitStamp before they can start buying again.
