MarketPress & MultiSite - How to pre-qualify shop sellers

We are setting up an "Etsy-like" site that allows people to set up their own shops. Does anyone know of a way to pre-qualify shop owners that we could integrate with the registration process? Above & beyond AntiSplog, as we are actually wanting to qualify that they are from where they say they are, or check their emails/phone numbers are real. Thanks for any help.