This is what happens when fuddy-duddy old line blue-chips, full of executives who don't even know how to use computers, suddenly decide that they have to take on the hot new shit (in this case, it'd be Amazon and eBay) and don't really understand anything about what they're doing. It probably never occurred to anyone that this would happen, much less that in the absence of any moderation it was certain to happen. Blah blah user generated content, and the shareholders' meeting is taken care of.
All that said the length of time it was up is pretty horrifying. On the other hand it tells you how many people are aware of Sears Marketplace.
(what's really horrifying is that the company who was THE retailer to early-to-mid-20th century rural America is so irrelevant that some shmuck sold T-shirt porn under their online banner for almost two fucking years and no one noticed.)