There is no doubt that inhaling smoke deeply into the lungs is not good for you. Any kind of smoke. Also, with the potent strains available now, there is definite impairment after smoking pot, so use before driving, flying, or performing surgery is a bad idea.
From personal experience, I can also say that perhaps the most insidious danger from smoking pot frequently is that it makes one perfectly content to do NOTHING. Oh, you might burn up the Xbox or make a killer pizza, and you're quite happy just lying in front of the TV or doing some trivial thing, but your motivation to go out there and live life and accomplish something gets put on the shelf. It's so easy to be happy doing NOTHING. That is the danger of pot.
OTOH, I do believe that no one should be in prison due to possession of pot. It's not a criminal offense. It's an offense against one's own future success, nothing more. It's clear that millions of people are going to grow it and smoke it, regardless of the law, so they might as well just legalize it and tax it. Shares of Xbox and Oreos will skyrocket, the government will have it's cash cow, and thousands of young men and women will at least not be convicts.
>>There is no doubt that inhaling smoke deeply into the lungs is not good for you<<