It was an unexpected reaction. Even if you believed the Short Euro and Long Dollar views were crowded due to the popularity of divergent monetary policy trades in the FX market, the extent of the EURUSD's rally after the ECB upgraded its QE program was exceptional. It was the biggest rally since 3/18/2009 and backed by the heaviest volume we have on FXCM record (futures posted the second most heaviest on its longer record). The question now is how much rally is there to this pair? That depends on how what percentage of the market feel it is time to back away from a clear fundamental bearing.