Independent of state (medical or otherwise) marijuana laws, employers still drug test (even in WA, where personal pot use is legal, for example). Pot users aren't a protected class for discrimination purposes, afaik. I agree that it seems silly.
Things are a bit different in the software world, where employers are moving away from drug testing because they need all the talent they can get. It turns out some potheads are actually pretty productive members of society if you give them a chance.