As I'm sure you're aware, http://ask.metafilter.com does the same thing. I use it because of the MetaFilter community: I have a general understanding of the demographic, morals, values and politics of the people I'm asking questions of. I also know that people's answers must be posted with an account they probably value because they have paid $5 to create it.

Do you plan to foster a community with certain features? Or are you looking for a broader range of people?