If the wisdom of crowds is truly operating on TripAdvisor then, while 760 million reviews can’t be wrong on average, most or even all of them individually can be wildly off the mark. And, of course, it’s the number of reviews on a particular topic that counts, not the grand total on millions of topics.

But enthusiasts for such sites seem to feel instinctively that some sort of averaging does need to take place, and that they can do it for themselves to arrive at an accurate result. For many reasons, they are mistaken.