After some research with other tradehill account holders, I believe Revalin is correct, that the majority of the bitcoins and currencies held by tradehill are being returned in their respective forms.  Thus selloff might not be only based on tradehill's liquidation.  It is apparent, however, that there are many exceptions, particularly where deposits were made in currency and not bitcoin.  It is certainly still the case that the dissolution of tradehill, one of the most popular bitcoin exchanges, does not inspire confidence in the market place.