There are 2 main concerns I have with marijuana being legal. I have a problem, like many of you mentioned with people driving while they are "stoned." Marijuana impairs a person's ability to act in a rational manner, much like alcohol does. It slows most people down, and they would not be able to make quick and critical decisions behind the wheel. The 2nd problem I see is people going to work high and putting their co workers lives in danger. The smell of marijuana can be hidden much more quickly than the smell of alchohol and the only way to physically tell if someone is high on marijuana (other than behavior) is to look for bloodshot eyes.
To be honest, it might make them more slow, but marijuana also make people hyper-aware in an almost paranoid sort of way. Also, the more used someone is to it, the less it affects the abilities. Not saying people should drive while stoned, just noting that studies have shown variable results from stoned driving.
What would I see to be the consequences of legalization?
Well, it would free up some tax money and rake more of it in; it would free up some jail cells, some police time, some court procedures.
Ethical bonus of stopping to arrest and harrass people who chose to do a pretty much harmless drug.
I would think that people in dangerous jobs would know better than to get stoned. And I would have no problem with a janitor smoking some weed -- it looks like a pretty boring and annoying job, so if the person can have a joint and enjoy the work, then all the best for him/her.
I'm pretty lax with these things and I don't believe that just because something was made illegal that would be the proof that it should stay illegal. If you look up the actual reasons of this ban, then you might also agree that many of them have been disproved.
Only thing: not to be sold to people under eighteen. Because science showed that it helped develop "addictive patterns" if consumed early, and it might have impacts on the brain and all. After eighteen, I'd consider that if you can drink, smoke evil tobacco and vote, you should be responsible enough to make decisions for yourself and smoke or not some weed, whatever.