P3P also provides other mechanisms to help customers and sites create private relationships. The P3P agent establishes a unique
cryptographic identity with each site, called a Pairwise Unique IDentifier (PUID). The PUID makes it more difficult for different
sites to share information since each site knows the customer by a different PUID. Since many recommender systems can make
recommendations based only on the users’ actions at the site, the PUID may be all the site needs to make useful recommendations.
Other recommenders require some personal information such as ZIP code or age. Customers may be more willing to share this
information though a P3P relationship, secure in the knowledge that they can create a new PUID in the future to "disappear" from the
site. Of course, this anonymity only provides protection through a purchase if the site agrees not to maintain a connection between
the PUID and the customer's real identify as needed for payment and delivery.