i smoke marijuana often, i enjoy it quite a bit and probably wont stop until i am a senior in college then im done. i probably smoke twice or more a day, but during the summer i usually only smoke once a day max.
i think its a fun hobby if you dont let it get in the way of your life and you can still be productive, i dont see anything wrong with it beyond that. i dont completely believe in all of the health risks as there have been studies from countries in which it's legal saying there is no correlation to cancer or to a shorter lifespan that they can find.
that being said it's not harmless, and can definitely fuck your life up like any drug.
everything in moderation, even moderation.