Once they put the service behind a paywall for the customers, they'll only end up putting themselves into the same market as Spotify and iTunes. In other words

Once they put the service behind a paywall for the customers, they'll only end up putting themselves into the same market as Spotify and iTunes. In other words, they'll just be a new face among the crowd in the market called The Competition, doing exactly the same thing as everybody else, yelling the same meaningless cant as all the other vendors. Not "share," but "buy." And if the competition's already doing better than BT and has a more established fan base and brand, well, roll the dice.