It's done through telephone and web conference (which shows the graphic presentation for discussion purpose).
From what I get, GreatDomains.com is working on a central registry of after-market (with Verisign REGISTRY) and will start charging listing fees while tapping into buyers who want to register names (not necesarily pre-owned ones). It'll be like when someone make a search at whois for a certain say zoobar.com, instead of telling them that this domain was already registered (and display the owner info), the new system will show that it is available for e.g. $300 instead of $35; very much like dot-tv's premium names.
It's really interesting taking this survey/interview both for getting some first-hand information from Verisign/GreatDomains and their $50