Imagine that you sell goods for bitcoins in a dollar-exchange rate linked way, and you have a sizable amount of bitcoins available. You have an income stream in bitcoins already, but if you let the price be too volatile you run the risk of having people wait to purchase for spikes in the market, so the majority of your income would start off with a slight exchange rate loss. If you have a projected growth curve for bitcoin, you'd be incentivized to sell whenever it grew too fast to try to mitigate your exchange rate risk.

I don't think this is what is happening, but its an example of an incentive that could cause this type of behavior.

-bgc