In May of 2012, we invented a healthcare re-targeting ad product. It worked by inferring what types of medical ads to show a user based on the type of doctors that they search for online.
Here is a video which describes the product.
The cookies would be set by the medical directories. The cookies have an ID that describes what type of medicine a doctor practices. For example, we know if someone visits a Dermatologist’s profile that we should show that user dermatology ads.