A while back I've posted about Austria's redneck web analytics "fight". Now it seems, that the British Telecom got in some kind of trouble for dropping Cookies to their clients. Here a part of what leaked from the trial:
"The report praised the invisibility of the system, observing that “only 15-20 trialists (0.1% of the trial base) identified the presence of the system and had a negative reaction”, but said that future versions of the system would be “100% transparent” (meaning undetectable).
While users can theoretically opt out of having their browsing tracked, the report noted that “the current [opt-out] method is cookie based to preserve the user’s anonymity. This will cause a user to be opted in again if they erase their cookies”. The report suggested that this feature be highlighted during the opt-out process."
Here more info about BT's web tracking trial.