I am thinking of where an end user would be. End users typically don't know much about domain names, so they're not going to be familiar with smaller marketplaces. So even if there was a domain name landing page service that also offered a marketplace, I don't think it would help promote or market the domain much.
That's why I was saying there is value in GoDaddy. Because many Americans, people who know nothing about domain names, will know of GoDaddy because of their brand recognition, so that will be the first place many will go to when they are thinking about buying a domain name. Once they are there, if they search for a domain name and it happens to be yours listed on Auctions, it will pop up and give them the option to buy. Because of GD brand recognition, people are then more comfortable and feel safe making a payment on their website for the domain.