You bring to light a very good point here. Many comparison shopping sites miss a lot of the best deals because they are only written to pick up data feeds from certain stores or the data they're pulling from hasn't been updated yet. Also, a lot of deals nowadays are found with bundles, coupons and rebates, which aren't picked up by comparison shopping engines.

Consumers should be aware of this and make sure they check out all sources to make sure they're getting a good price. Deal websites are a good place to look, but many times the deals are for random things and are not relevant to what the user is looking for. A good list of deal websites can be found here. (http://probargainhunter.com/2008/11/05/popular-deal-sites-october-2008/)

I work for Wishabi.com, a website that has come up with a solution to this. At Wishabi, users create a wishlist and our community of deal hunters post deals for these items from all over the internet. Users are they notified when there is a good deal on any product they are wishing for. The deal hunters are paid by a commission sharing structure at Wishabi. Users know they're getting a good deal because we have a deal-rank algorithm that rates each deal based on numerical and user inputted variables.

Hope this helps