I tell people all the time. Legal weed will be theo worst thing for older smokers. Young ones in HS/College who dont yet care about jobs no big deal, its better. They will be able to buy weed and even 6th and 7th graders will have no problem buying it from SR's that turn 18. My nephew just graduated and told me he knew a couple kids at his HS that got med lic, already 18, and would buy the weed then sell it at school to the kids not yet old enough to go to the shops.
But for adults they will make it .5 nanograms to be DUI which means most regular smokers will test positive even without smoking. They will let companies say no job for pot smokers so you won't be able to get good work.