In my opinion Fab.com is the next step in the evolution from the daily deal websites. The main difference is that currently it focuses on delivered goods while daily deals were about services in your area, but I think their basic hypothesis is that people love deals and will spend money in things they didn't consider buying just because the price is good.
Another difference which I noticed is that unlike most daily deals websites, theirs are not time-limit based, but rather quantity-limit, which I guess works better for the suppliers since there cannot be a situation where they have to honour more transactions than they could have foreseen.
As a customer, I also noticed two main operating models which I find interesting. The first is where Fab.com have the items in stock and the other is that the items are delivered to fab only after you have made the purchase, and sometimes within a week of ordering, which might mean that they are waiting to make a bulk shipment from the supplier, and perhaps don't have to pay for the goods until they have orders.
Another interesting feature they have is they give you 20 minutes to checkout. This, I guess serves two purposes, the first is giving the customer a sense of urgency, a "buy it now or lose it" feeling, and the second is that this prevents blocking people from buying the product just by having it in your basket (since quantity is limited).
There are already quite a few clones which I have seen seen. One is monoqi.com, but I have seen others (just don't remember their names).