Maizey, unlike GAOTD, I think WOOT! is a "supplies limited" operation as well as being on the 24-hour clock. The old saying - "you snooze, you lose" - applies.
WOOT! seems to be an off-shoot of a trend to reduce inventory of and cut losses from perfectly good but unsold items. I could be mistaken, but it appears to be a tad/teenybit/smidge more upscale than the credit card companies stunt - sticking "(inflated) value-added" piggyback specials in monthly account statements to a captive sucker audience - "FREE GIFTS" (read crap) for "just the cost of shipping". WOOT! seems the equivalent of remaindering books in $1 bins. It seems to focus on retail products and targets impulse shoppers.
I'll put it in the same category as the larger (and pricier) Overstock.com, with the hook being their 24-hour window. Overstock uses "limited time only" spam to create a sense of urgency. Then there's the infamous QBC (if they're still in business)... they hyped crap hour after hour to people with shopping addictions. At the bottom of the sludge pond are late night infomercials. They hawk stuff that even crap finds offensive. (e.g., coral calcium supplements, colon cleansers, get rich quick in the stock market, swampland for sale, MLM scams, etc.)
FWIW, another part of the inventory reduction trend are companies that specialize in matching wholesale inventory to businesses/builders in search of supplies and products. It's a great way to reduce landfill demand and it reduces tax write-offs a bit, both positive for Joe Public.