Tracking Users site to site growing in EU--fueled by Ad Exchanges--Threatening Privacy

Retargeting--following people site to site--is growing in EU as a result of growth of ad exchanges there.  See Criteo mentioned below, and check out Google's case study with the company that specializes in stealthfully shadowing people online:

excerpt:  It is now possible to buy European inventory through the exchanges and SSPs. They have done an excellent job of aggregating supply and making it available in real-time. The significance of the Microsoft and Hi-Media deals can’t be underestimated on a pan-European level. The UK, Netherlands, France, Spain and Germany are all in play now. Companies like Criteo have been quick to seize on the new opportunity. It is the biggest trader on the exchanges, and has scaled a significantly-sized business across Europe (let’s say $140 million run rate in Europe) over the past two years.
from:  The Great European Opportunity: Why Ad Trading Is Now Making Scale Possible In Europe.  Exchangewire.  21 October 2011.