The fact that you had to preface this with you and your friends being pet owners kind of does make it a special case. You being suggested this vacuum cleaner by Amazon after buying it also doesn't do anything for you in this scenario because you bought the same one for your friends, so the recommendation wasn't needed. I think people are losing sight of the original argument which is that Amazon's recommendations can sometimes overemphasize recent purchases with very little context around what the items are.