With regards to advertising, perhaps the crowds aren’t so wise after all:
The centrality of advertising to the new digital hive economy is absurd, and it is even more absurd that this isn’t more generally recognized. The most tiresome claim of the reigning official digital philosophy is that crowds working for free do a better job at some things than paid antediluvian experts. Wikipedia is often given as an example. If that is so—and as I explained, if the conditions are right it sometimes can be—why doesn’t the principle dissolve the persistence of advertising as a business?
A functioning, honest crowd-wisdom system ought to trump paid persuasion. If the crowd is so wise, it should be directing each person optimally in choices related to home finance, the whitening of yellow teeth, and the search for a lover. All that paid persuasion ought to be mooted. Every penny Google earns suggests a failure of the crowd—and Google is earning a lot of pennies.Lanier, You Are Not a Gadget, page 82
One response: part of the purpose of advertising (perhaps the most significant purpose) is to persuade you to purchase things for which you have no need whatsoever. Perhaps the crowd does not guide you towards the best tooth whitener, not because it is unable, but because it rightly sees no need for that.