(1) The Feds decided they're tired of being the bad guys. States where medical marijuana is legal get to enforce the law themselves. Or not.
(2) Maine is wrestling with this issue, simultaneously with the gay marriage question. And at least some fraction of the kiddies voting in an off-year election to stop gay marriage are not going to be all that interested in heavily regulating marijuana. This does not surprise me. My parents are horrifically anti-gay, but they've been known to state that marijuana should be legal and regulated because it would be a lot cheaper that way.
The article concludes by noting that the way forward to complete legalization at the state level is now open -- which is further indication that the pendulum is swinging away from the Reagan legacy. I would merely add that the article fails to take into consideration (when mentioning the state benefitting from saving money on enforcement and possibly collecting taxes on marijuana) the potential benefit to farmers. Marijuana is an amazing cash crop. A land-pirate state that legalized growing it and turned a blind eye to people shopping it across a state border could make money on a level that would make casinos (even in their heyday) look like small fry.
Of course, that might attract federal attention.