Woot is a liquidator, not really related to Groupon, LivingSocial, et al. Liquidators have existed for eons, Woot simply brought it to the general public - instead of dollar stores and cheapo stores.

Maybe Woot is the post-Groupon. After you Groupon'ed your business to death by slashing your revenues 75% at a time, folks like Woot get to sell off the skeleton. As long as businesses keep failing and inventory management keeps sucking, Woot will have plenty of business.

That's actually a thought though: a lot of liquidation inventory comes not from outright failing businesses but just really poor demand forecasting and logistics. With improvements in these fields Woot may find it harder and harder to source compelling products.