Why do so many people claim that marijuana is not addictive and harmless?

This is a good question . . . it's the same as people who are drunk and cannot speak right, falling over, drinking and driving and saying "I don't have a problem, I just like to have a good time. I could stop drinking if I wanted to." Is Mary Jane a serious drug? No. Is alcohol a serious drug? No. Are they abused on a regular basis, yes. Some people can use these recreational drugs somewhat responsibly (at home, with no driving or use of tools, or in situations where they need to use their brain), and some people even use it to control their medical/psychological conditions, but a simple fact MJ does affect you short term and long term. It's scientific fact. The people who are claiming that it is complete harmless are under informed and most likely frequent users trying to justify it. Good for you for never having smoked it, keep up the good work!