The great game is over! Well not yet but it seems the business utility of Twitter may have waned somewhat after they trottled back the feedback loop. However...
[update]
I looked again at these number and realised that they actually run over Thanksgiving in the US. Our users stats also went down in that period - the first week in 14 consecutive weekly rises so the correlation appears to be with the holiday period not necessarily Twitter's change.
Once again, the stats prove nothing.