It really doesn't matter whether the traffic went via a domain, a Google property or a publishing partner. Everything is tracked and recorded each step of the way by the Google number crunching system. I enjoy playing poker and it can be a good analogy that may expose some of the weaknesses in Google's informational armour. Let's imagine that Google is playing Texas Holdem with all of the parking companies.
Once all of the cards have been dealt the player representing Google calmly gets up and walks around the table looking at each players cards. All the other players are asked to hold up their hands so that the Google player can get a better look. This similar to having the informational advantage that Google has carved out at the moment.
The information gained from this walk is invaluable but does it allow Google to win the poker game? After a couple of hands a few of the players get sick of being beaten due to the Google players unfair advantage and decide to join another table. This happens to be the Yahoo table. This also means that there are less players around the poker table at which Google is playing.
The first challenge for Google is that just because you have perfect information doesn't mean that the other guy won't leave the game. In order for Google to maximize revenue they need to ensure that everyone wants to play poker with them.
If all of the parking companies decide to leave the poker game at the same time then Google's perfect information doesn't help them at all as there isn't a game being played anymore and Solitaire isn't very fun when compared to poker.
Source: Written by Michael Gilmour on Whizzbangsblog - Reprinted with Permission on DomainNews.com - June 5th, 2008