Meh, in my opinion people can do all the drugs they want. It's a matter of free choice. Everybody knows the effects of the substances they put in their bodies, so if they want to, they should be able to. So long as information about the substances is readily available, why not? I hold absolutely no prejudice for people who smoke pot, take cocaine, etc. I personally don't take drugs but if someone is willing to pay for them and take them, they have every right to.
As soon as this happens, however, society will no longer be required to aid these people should they have problems. If someone decides to take heroin and becomes a habitual user and ends up losing all their money, they no longer have a right to a government-paid rehab center. Let's face it, why should people pay for the decisions of others?