Cool thing about the Web:
Users can browse anonymously and sites can offer customized content or advertising
without any personally identifying information!
Service may ask for two forms of anonymous ID (PUID and TUID)
- similar to cookies but more restrictive.
- under specific P3P control: must be asked for as part of a proposal.
- explicit difference between information used for one session (e.g., shopping basket) and
for information used at a site over time (e.g., to idenity myself to a yellow pages site).