I think it's useful for predicting momentary trends but nothing long-lasting. For example, it was useful to show the effect that the Bayonetta 2 Direct had on previous pre-order numbers (with spikes upwards of 200% in some regions), but it's not useful for saying "OMG BAYO 2 TO SELL 7 BILLION UNITS LOL". People who do that are honestly stupid and deserve to be ridiculed forever.
NNID: TheCCluc