I've been long amazed at how bad Amazon's web ads are, as if the department was authorized to get rid of money as fast as possible. Besides the times -- because of one click through to a joke product like $10K ultrapremium audio cables -- that I would get followed by weeks with absurd ads, my favorite example is getting barraged by Battlestar Galactica season 3 ads right after I bought the damn thing. OTOH, perhaps Amazon's ad/recommendation system was too smart, trying to warn me from purchasing season 4.

I understand that big data learning systems are harder to tweak than what we'd suspect from ground-level day-to-day experience. But it just seems like Amazon still has plenty of room to apply some conventional heuristics to get far more efficiency than they do now.