I think of Double Click as an identity company. An intermediary that builds and brokers models of users.
The clever bit in their approach is that they build these models without having to solve two of the hard problem two problems. They avoided the problem of getting the installed base of client software to change. They avoided the problem have building strong respectful relationships with the users being modeled. You could argue that they turned both these problems on their head; leverging both turning them into advantages for their business.
These problems are both of a kind. They are both hard because the numbers are huge and the benefit for solving them one user at a time are low.
These probelms have a facinating complementary nature. People who work on identity tend to focus on one or the other. People who focus on the need for vendors to create really strong relationships of trust with their users tend to roll their eyes when you suggest impoving the installed base of client software. People who labor to raise the bar on the client side tend to paint stark exagerated pictures of how nieve it is to expect to ever create high trust relationships between weak users and strong intermediaries.
Of course it is the lack of any relationship with the users being modeled, that makes DoubleClick smell so evil. That they conspire with sites to leverage client software cookies enable their model building is just the means of that evil.
I see they are in play.
Here’s a puzzle. If you were king of DoubleClick could you create the missing solid user relationship.
Notice one more thing. A third hard problem in the identity problem space is how to create the governing rules for your circles of trust. Note: DoubleClick has proably got the largest existing “circle of trust.” Good use of scare quotes, huh?