> (because it has no real downsides)
Ohhh boy. On this throwaway to say otherwise. I'm sorry if this post is a bit incoherent because I'm horribly tired, still getting past the nuts insomnia phase of quitting.
I've smoked a lot of weed. Started smoking in high school, heavily when I was 19 until a couple weeks ago (I'm 26 now). About an ounce a month over that time, sometimes two ounces. First it was for insomnia, then it was supposedly for my digestive health (actually, quitting gives you gas and loose stool), then for anxiety, sometimes for aches and pains (which were made worse because of poor posture -- it is a muscle relaxant, after all). At the end it was for my paranoia, so to speak -- I was convinced I had cancer setting into my guts and that it was the weed that was keeping it in remission. They did some experiment where this worked with rats, right?
Right now it seems like there are no side effects. Trust me, there will be. Your memory will turn to shit and you won't be able to follow a conversation. You will try to remember a number and forget it moments later. You'll be slow to recall your own zip code. This doesn't just happen when you're high, it'll happen the day after smoking also. Basically, if you're feeling "all right," you'll have these effects too.
You'll become dull. You'll sit around with peers and have nothing to talk about, just a stupid smile. Now, you'll feel totally at peace, but you're a basically a human blob, incapable of really interesting thought.
Your thoughts themselves will become lazy, less rigorous. You'll think you're being "chill" when you quit a debate, but really, your mind is just working much slower.
You'll edit code pointlessly, shuffling stuff around.
It's not all bad -- the ability to come up with really funny insights doesn't go away, so you can make people laugh. But there's no depth to anything you do.
Heavy smoking makes you shiftless too, and easy to abuse. It let me stay in an abusive marriage for a few years, fun (I sort of knew this but was too embarrassed to leave this woman I'd just married, so I smoked more to keep my sanity). Only when I tried to slow down smoking for a little while did I realize how bad things had gotten. Whether or not you believe it's happening, people will try to take advantage of you, if you're worth taking advantage of.
Keep in mind I'm not talking about "smoking every now and then when I feel bad," I'm talking about daily use: A smoke in the bathroom before you shower for work and constant smoking every night. Lunch break smoke if you're a real go-getter. Maybe smoking on your commute. Always making sure you have a good bit of bud or hash oil before you go on a trip anywhere (I remember smoking in a company's garage in SF after a tech meetup, and also regularly taking smoke breaks in my employer's garage in a less tolerant state).
In this industry, people will let you get away with it if you're any good, because the fact is that a half-baked person who can still write decent, reliable code is 10x as valuable as an regular guy with no skill/aptitude/motivation. And as you might have noticed, most people don't take to this stuff all that well, which is why (compared to other working schlubs) we get paid pretty well.
Also, YMMV, but it completely robbed me of my sex life when sober because I'd orgasm so fast.
It took several years of heavy, daily smoking for these serious symptoms to fully manifest into what seemed an indomitable form, probably when I was 24-25. I know for sure that heavy daily smoking of high-grade buds in California took it to the next level.
I had to stop smoking. I realized how stupid I'd become, even if I was raking in the dollars (not doing consultant BS either, senior developer stuff at a good tech company and respected by my peers).
Holy crap, I'd forgotten how smart I was. Suddenly I could remember everything. Issue numbers. My train number. Dates, times, places. I could remember things (addresses and stuff) I learned when stoned, knowledge I didn't know was in my head. Weird!
Now I can't imagine smoking again, except rarely with friends. Having my brain back is so wonderful. Feel free to ask my questions, though I probably covered the uninteresting life of a stoner programmer pretty well here.