...but Addicting -is- a word. Granted, 99 times out of 100 it's used incorrectly, but the word does exist and can be used.
Take the word 'abuse' as an example. 'The husband was caught abusing his wife' - 'the husband was abusive to his wife' - 'the husband abused his wife'.
'Addicting' is also listed in the OED, which to me is far more reliable a proof than someone just saying it doesn't exist.