I think those are very different marketplaces, solving different problems. Still, this is why Amazon shows ads from other retailers on their site.

Fab was selling what's cool, and creating a price incentive. But for their audience, cool is actually more important than cheap, so by promoting the makers of cool (all of whom also have their own e-commerce channel) they were eroding their own business.

I'm not suggesting that was what killed them. I'm just saying they didn't have a bulletproof model before they started taking crazy pills.