Your criteria for what constitutes an "expert" seems to privilege individuals who have been approved by some segment of the dominant culture, e.g. the academy, the publishing industry, the entertainment industry, or other such institutions. There is no lack of opportunity to engage in "conversations" with people who already have such platforms. What is necessary is the opportunity for dialogue with people who are thoughtful but whose ideas may not be in the mainstream, perhaps because they are avant garde thinkers, perhaps because they are not interested in publishing or fame, perhaps because they have been marginalized by the dominant culture.
How would you evaluate the expertise of someone like Greg Mortenson who is exceptionally knowledgeable about Central Asia because of his personal interactions. Prior to his being on the cover of Parade magazine and the publication of his book, would his accomplishments have qualified him as an "expert?"
In the category of Faith and Beliefs or Life and Death, will the "experts" be only the Deepak Chopras, or will we hear from shamans and healers? Who will be your "experts" on poverty? on being a single mother? Is Gloria Steinem more of an "expert" on feminism than hundreds of other women who have experienced and thought about sexism, just because Steinem figured out 40 years ago how to get media coverage?
If this site is really about "thinking" and "ideas," then why do you feel "expertise" needs to be vetted through institutions that depend on popularity and peer review? Why not let the ideas speak for themselves? In fact, why have experts at all on a site like this, which seems to want to be about dialogue by thoughtful women and men?