I don't think it's that bad of an idea. But I'm not sure why it should be open for everyone, beside revenue through taxes. There's a couple cases I'm familiar with where people have had severe pain, I'm talking about results from head-on collisions, and have used medical marijuana to ease the pain. And it helped.
There's a strain for every pain. But there's people who just want to get stoned out of their mind. I support the use for people who actually could use it, but I can't support it for people who want to smoke just for the sake of doing it.