That Grady's reviews tend immediately to accumulate a mind-boggling number of 'helpful' votes is one thing. But have you noticed that after this initial buildup, the vote count tends to stay static? That is the voting rate on his reviews has two patterns: intial two-three days, when it's huge; and the later one, when it pretty much dwindles to nothing.
It seems that the items Grady reviews are somehow more (much, much more) visited by potential buyers/review-voters in the first two-three days after the posting of a Grady review than at any time afterwards. How could we explain such an uneven interest from the consumer society?