Yahoo announce this week that it would anonymize search user data (in most cases) after only 90 days.  That’s significantly less than Google or others – some of which until recently retained it for a couple of years.  There has been a lot of pressure to reduce the amount of time that user data is retained.  Those that want to retain it longer say it is needed for the user experience. 

Of course its all about the details, and how anonymous it really becomes, but the less info that is retained about individuals, the better.  Like many things it is a balancing act – some info retention is needed to provide services – the tough practical issue is how to provide the services but at the same time limit the amount of personal information retained, and how long it is retained.