James Surowiecki's argument about the remarkable Wisdom of Crowds depends on the crowds being diverse. The kind of diversity that matters is that the members have a variety of experiences. That way, the errors made by some individuals with certain kinds of experiences are cancelled out by the errors of other kinds of individuals with different kinds of experiences. The result, by Providence I think, is likely to be more accurate than the judgment of any one group -- even the experts.
The diversity that counts is a diversity of experience. Crowds that merely look different, but think alike, don't count.