These companies can also track you by IP address. I've had conversations with co-workers about them considering a specific large purchases, and then seen ads fo

These companies can also track you by IP address. I've had conversations with co-workers about them considering a specific large purchases, and then seen ads for what we talked about popping up. I'm assuming that if the CPM is low enough, many ad-retargeters will take the risk of targeting ads based on IP address alone.