Personally, I'd use a TiVo or DVR regardless of sharing of viewing habits, but that's just me. It's that life-changing...
" The TiVo DVR collects certain types of information from its users, including
Anonymous Viewing Information, Diagnostic Information, Commerce
Information, and Service Information (each as defined below).
TiVo has no way to access any of your Personally Identifiable Viewing
Information (as defined below) from your TiVo DVR without your prior
consent. Absent your consent, TiVo has no way of knowing what shows you-as an individual or household- have watched, recorded, or rated with Thumbs Up or Thumbs Down. ........
TiVo does collect Anonymous Viewing Information; that is, information
about viewing choices made while using your TiVo DVR, but that does not
identify you as an individual or household. In other words, there is no personally identifiable information associated with your Anonymous Viewing Information that could identify the Anonymous Viewing Information as coming from you or your household.
TiVo also collects Diagnostic Information from a small number of randomly
sampled TiVo DVRs for quality control purposes. If you subscribe to the TiVo
Plus service and don't want your Anonymous Viewing Information and
Diagnostic Information used in any way, simply tell us ..."