As far as I know the only purpose of "activation" is to prevent fraud. Otherwise the cards would be active as soon as they were swiped through the register.
How can it prevent fraud? If the assumption is that nobody can acquire the number other than the owner then it doesn't prevent fraud, while if the assumption is that the number could be copied or stolen from the owner then this could still happen after the owner activates it. I think they enforce activation to track users not to prevent fraud. I also already answered all fraud related questions and demonstrated why this cannot be a fraud case. I'll be happy to answer any specific doubts or scenarios you got.
My problem was with automatic system not "hearing" the virtual dial pad because of my bad connection. As already mentioned, anyone can activate a card anonymously using a free skype account or free websites which call 1800 numbers without charge or even signing up. Tor could be added as an extra layer of anonymity too.