First we all gotta separate addiction into two different categories: physical and psychological.
Psychologically, of course its addictive. Like everyone has said, anything pleasurable can become psychologically addictive.
I think what the big argument here is whether or not its physically addictive. In EVERY neutral party that I have read, it said weed has a very low physical addiction. Keep in mind, this is lower than every other drug out there (caffeine, alcohol, nicotine, etc.). But, it is mildly addictive. The big example for this is how an experienced toker needs more weed to get high than someone who is completely new. Tolerance is a big sign of addiction.
Also, most people I know (myself included) who are everyday tokers will experience withdrawls generally opposite of weed's effect. Things like lower appetite and such. Again, since the physical addiction is so low, the withdrawls are as well. It could be something as simple as a headache that people will just pass off as a natural occurance. But... its still there.
Hell though, the addiction is so damn small that it doesn't matter. I mean, sugar is probably more addictive.