Yvain says in his posts' comments that coffee doesn't work, as tolerance builds up. This seems disputed.
But why not ban coffee? Because, like alcohol, it's now too ingrained in our culture. But if it wasn't - preventing headaches, irritability, concentration troubles, and the expectation that everyone can pull all-nighters? Fuck yes.
Coffee may be too Near to discuss; I suggest a different even-older expensive teeth-staining addictive stimulant plant popular in social gatherings.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.