I wouldn't be so fast to marginalize one habit over another. Marijuana might not be physically harmful, but I do think its a fair assessment to say that some people use it to excess and struggle controlling their use. This also can be applied to video games, internet browsing, food, and so on, but it doesn't make the issue any less severe for those who seek help.

Not to mention that when Moores law was coined, miniaturization (in the context of computing) was still relatively primitive. I highly doubt we are going to see transistor density grow at that rate ever again.