First of all, follow reality and not our stupid laws. Science indicates that Ecstasy is the safest recreational drug and the least habit-forming. The next tier is alcohol, pot, cocaine (although based of everything I've heard personally pot is safer than the other two). With these, there are plenty whose use of them is not a big issue, some who overdo it, and some addicts. The next tier is heroin, meth, seem to always lead quickly to addiction.
Every dollar you give an addict is another nail in their coffin. I might be a custy to an addict if I thought she might do something bad to get the money. But let them go into withdrawl first. An addict is more likely to go to rehab if they see they won't be able to feed their habit steadily. Usually it's not a issue for me cause addicts look like hell. I prefer to make my charitable donations in a way I can get a tax deduction for it.
If someone's not an addict, I don't feel like it's my business. Although the line between addict and heavy user is not always clear.