My thoughts on this are that if you want to use a substance like this and take the risk of whatever health effects it might cause, go right ahead. It's your body, you can do what you wish with it.
This doesn't apply to all drugs. There are plenty of drugs out there that will leave the user willing to commit any sort of crime just to get their next fix. So those drugs do present an unacceptable risk to society as a whole. Marijuana, not so much.
That being said, there are way too many unknowns and too many studies indicating negative side effects for me to want to try it. But that's my choice. I'm not going to tell others what they can and can't do so long as it doesn't affect others.
Ultimately, I say treat marijuana as similar to alcohol. Don't sell it to minors, don't use it and drive, and don't be surprised if you get fired if you show up to work under its influence. You want to use it at home or other private place that allows it? Knock yourself out.