Isn't that in return a copy of DC killing Superman years ago? Which in return was a copy of Marvel killing Captain Marvel before that? Which in return was.....
The actually rather large print detailing the Unlimited data use part of the iPhone tariffs does state that you can't use the SIM in another device, so O2 would be well within their rights to start charging for access if you put the SIM in an N95 or a data card.
There's more than that between the Web and Web Max. The Web Bolt-on prohibits use of the phone as a GPRS modem for a computer, the Web Max doesn't, so even if the fair usage limits are lifted, there's still a difference.