Not sure about the addiction part, but as well as not hydrating your body, the acids in cola (average pH level of between 3 and 4) can rot your teeth and can cause your stomach acid to become, well, over-acidic. This means that too much can be very bad for you.

All colas can also colour your teeth a very distinctive dark-yellow colour, as can tea and coffee if you over-indulge, so be warned.