The equivalent of this is showing gaming keyboard ads on ign.com, and bank ads on bloomberg.com. As long as same ads are shown to every visitor, this is no problem at all.

The people hate it when their actions on one site affect ads on completely unrelated sites. Real wold equvalent would be a salesman saying "I was passing by your house yesterday amd noticed you got a new bed.. Want to buy some bedsheets at a great price?". I think we agree this would be super creepy.