Phorm / Webwise is a disgusting ex-spyware maker now intent in profiteering from your browsing habits without your consent, as described by this exhaustive explanation of the Phorm system and why it is bad for everyone. They will basically spy on all your network request and then inject their own advertising on somebody else's pages. This is bad for users (spied on without consent, with very low guarantees of anonymity), and extremely bad for any website holder (whose content is modified and exploited, again without consent, and probably infringing copyright laws).
Yesterday the European Union, usually so despised by British citizens, formally accused Britain of infringing the EU directive on data protection by implementing Phorm. Today, Amazon opted out of the system, as previously did Google, Facebook and many others. I personally opted out a few minutes ago, by sending an email to firstname.lastname@example.org listing all my domains.
For the sake of the net, Phorm/Webwise MUST fail. If the system goes live, I will ask my ISP whether my traffic will go through BT, and if so, I will switch to a provider who can guarantee they will NOT take part in the system (i.e. not Virgin and not TalkTalk).