That part is a bit of a bad joke, but I've known people who have lost chunks of their lives to WoW, and the criticisms you outline for cannabis seem to mirror my perception of WoW very closely—"addictive", "causes them to be extremely unmotivated", and "a lot of people end up really trapped by it".
To be honest, when I was in college, I was more worried about the potential dangers of WoW than I was worried about cannabis or other recreational drugs, chief among them alcohol and caffeine, but also cannabis. I had a "just say no to WoW" attitude.