Another possible reason they failed - What a horribly, horribly slow website.

After reading this article I visited fab.com as I'd never visited before. Saw some interesting products, some I might buy, but loading a single page of items shot my fan speed up and froze the page for a good 7-8 seconds while what I guess is their javascript "enhanced" the page.

Awful, awful user experience. I couldn't last more than 3 pages of items before giving up. It doesn't matter what your product is if you annoy the hell out of your customers with badly designed technology.