It's a pseudonymous model in which we know a certain profile corresponds with a particular browser. That browser may be used by one person. That browser may be used by multiple people. The computer may be used by multiple people. If you were to visit, say, a travel website, a cookie might be dropped onto your computer by BlueKai or another company. That cookie does not say, for example, Alan Chapell. That cookie just says, “interested in travel to Hawaii”. There is no way to identify the user based upon “travel to Hawaii”.
I imagine a vacation in Hawaii would look pretty good to many in this room right now .