So, Phorm's offspring has gone mobile, then?
Given that Phorm-style technology can work both ways, a careful read of the article would seem to indicate so: According to the article, O2 customers who were surfing the web on their phones via Wi-Fi were not affected, but those who were surfing through the O2 network were affected.
Given that two given HTTP requests to identical static URLs/pages hosted by the same web server should be semantically identical, the fact that they are not indicates that O2 is doing some on-the-fly request header rewriting.
So if O2 is rewriting outgoing requests, how do we know that it's not rewriting inbound responses?