Yep, I never denied that it's addictive.
But it's not addictive on the same level as chemical-based dependency as alcohol or drugs, it's more a habitual and reward-based addiction like gambling. It's easier to break out of in a way. I know I was addicted for a long time when I was 22 or so, I'd spend every day logged in, as soon as I woke up, until I went to bed - so 12 hours or more per day!
Broke my addiction by quitting for all of Wrath to go do my Masters, but I love the game too much because it's something I do with my friends! So, I came back, but I do not play every day anymore. I log in mostly for raids with my guild or if I'm really bored, to go do some LFR (casual raids) with my alts.