Yes, smoking can be bad, but its not as big a deal as those commercials make it out to be. I don't do it personally but a lot of people I know do and they say its hard to quit. I'd say try to quit because it is bad, but if you can't don't think you have a 90% chance your gonna die, you can, but to much McDonalds will kill you to.
P.S. Happy Marijuana day!