In two weeks time, Valve will be retiring nine of the earliest released TF2 hats. They will no longer be able to be obtained by any method other than trading existing copies of them. It seems that the prices of them are also shooting up in light of their soon to be rare status.

It's an interesting change, and I can't help but think it's been motivated at least in part by Valve's recent interest in the economics of their games, especially with the hiring of their economist. The creation of this scarcity is likely to provide some interesting data to analyze, so it's not unfeasable that some writing will turn up over at the Valve Economics Blog in the future.