The Penny Arcade Report have dragged up something interesting. PA have had a sit-down with the game research company EEDAR and gotten some data on the importance of positive reviews:

"...the results are startling: a game with an average review score in the 90s will sell three times as many copies as a game rated in the 80s. Lower scores can sink a game. The influence of game reviews also extends into word of mouth and user reviews. The critics have more power than we thought."

Read the whole article here.