Well here’s something interesting. Reading the comments here -
http://www.politicalpenguin.org.uk/blog/p,297/#comments
Note comment 7 is a response from someone on the tech team at
techteam@phorm.com
The part that interested me was this,
“Re the opt out, if you opt out  or switch the system off, it’s off. 100%. No browsing data whatsoever is passed from the ISP to Phormâ€Â
So they say that once opted out that no data passes to Phorm. Interesting. Still don’t believe it, but interesting statement nevertheless.