For your second point, yeah, it's probably a good idea to research anything before you ingest/inhale/inject it. High-fructose corn syrup, I'm looking at you :)
Your example doesn't bring anything new to the table. I know people who function well in spite of playing World of Warcraft and I know people who temporarily ruined their lives playing WoW. Was it WoW's fault? Should we make WoW illegal? Should we make everything illegal because it might lead to devastating consequences?
In process of experimentation, I created two rules for myself: a) You can't blame your fuckups on the drug, even if you were under the influence. b) You don't have to mention that drug helped you, if you created something good.