I think it eventually will be legalized in certain states. Eventually your going to have so many people like me out there, who fucking hate the government, they'll take control of the state legislature (maybe in new hampshire) and just give a finger to the feds, they've really overstepped their bounds, they have no right to tell people what to put in their bodies.
Like many people have already said, negative effects on your life constitutes abuse. Here's the kicker though, I think your abusing your brain if you don't smoke weed every now and again, I think your abusing yourself if you don't read a lot, I think your abusing yourself if you don't try Salvia and shrooms.
Salvia and shrooms really enhanced my perspective on life, one of the main reasons I love weed is the way music sounds when I'm stoned, and the crazy conversation that comes up between friends.
Can you abuse weed? Fuck yah, but you can just as easily be abusing other things, like your brain, by not reading, or doing shrooms
, or your body by sitting on your ass all day. I figure we're all abusing something, so whats adding one more to the list eh?