I smoked weed lightly to heavily, for ten years. I wish I had never even heard of the stuff. It's not for everyone. Especially not people who need to be on psych meds, instead. Luckily, that's not me.
The problem with a band even considering calling themselves "420 friendly" is that you will spend time and money pursuing that activity, instead of concentrating on what is important. The music.
Once you light up, you usually drift over to the Xbox. Then you spend valuable practice time shooting zombies or racing Mario kart, or whatevs tha kidz is into these days.
It can also affect your judgement, when it comes to your overall sound, as well as how your individual parts and tone are coming together. As a former user, I'm amazed at the difference between how great you think everything is when you're high, and how lousy most things are, when you're watching potheads revel in their awesomeness. You owe it to yourself to check out everything you do, in a sober state.
Yes, Up In Smoke was a classic. When you do it, not so much. People have seen it and heard it all. Ad nauseam. It's not as original as it was in the late seventies. Just celebrate your new weed-friendly political climate, and try to keep that stuff to yourself.