I like that you have the ability to exclude on some dimension (eg, I don't use Amazon.com). Do you have or are you considering adding more retailers beyond the four you mentioned? For example, I buy a lot of unroasted coffee from sweetmarias.com, and excluding Amazon from Popgot results eliminates all but one listing (from Walmart).
Ah, hell yeah! My buddy on this project has been itching to add sweetmarias.com ... he just needed this as an excuse.
So yeah, we'll add it. If you shoot me an email (or post it here?) to chris @ <our site>.com I'll send you a link when it's done. Should take a day or two.
