Professionals are no longer needed for the bare purpose of the mass distribution of information and the shaping of opinion. The hegemony of the professional in determining our background knowledge is disappearing—a deeply profound truth that not everyone has fully absorbed.
In their view, Wikipedia represents the democratization of knowledge itself, on a global scale, something possible for the first time in human history.
As wonderful as it might be that the hegemony of professionals over knowledge is lessening, there is a downside: our grasp of and respect for reliable information suffers.  With the rejection of professionalism has come a widespread rejection of expertise—of the proper role in society of people who make it their life’s work to know stuff.
For instance, journalists, interviewers, and conference organizers—people trying to gather an audience, in other words—use “expert” to mean “a person we can pass off as someone who can speak with some authority on a subject.”  Also, we say the “local expert” on a subject is the person who knows most, among those in a group, about the subject.  Neither of these are the very interesting senses of “expert.”
To exclude the public is to put readers at the mercy of wrongheaded intellectual fads; and to exclude experts, or to fail to give them a special role in an encyclopedia project, is to risk getting expert opinion wrong.
If we reject the use of credentials, we reject all evidence of expertise; ergo, lacking any means of establishing who is an expert, we reject expertise itself.  Meritocrats are necessarily expert-lovers.
Experts know particular topics particularly well.  By paying closer attention to experts, we improve our chances of getting the truth; by ignoring them, we throw our chances to the wind.  Thus, if we reduce experts to the level of the rest of us, even when they speak about their areas of knowledge, we reduce society’s collective grasp of the truth.

via On The New Politics Of Knowledge | Conversation | Edge
On the brighter side of it, we are for the first time able to participate in many things. Just being trained in a discipline (PhD?) does not automatically create opportunities for one in the old system. But in Wikipedia it does. How many people who have PhD do get an opportunity to write a text-book or a popular article? I would like to ask how many of contributors on Wikipedia are really subject experts? There might be many, and they would be able to point at the right evidence, when needed to “show off” their authority in the field, which the normal user won’t be. So what’s the fuss about?