As a technology expert only, Tim Berners-Lee should not be attempting to determine aspects of the UK rehabilitation of offenders act (or any other country). Where did he pluck '10 years' from? Recent changes to UK law means convictions are considered spent after much less than 10 years now. Standard criminal record searches would not show minor crimes after this time, but a google search would. It seems the internet over time has become a new criminal record bureau with no concept of a spent conviction.