Taking this substance out of the hands of the black market is the most responsible thing that can happen.
However!
A slow legalization would be better for our companies than a fast mass legalization.
States sign on one by one, let these fledgling companies get their roots down and secure a large structure. Then when Feds finally legalize we'll have less chance of big businesses coming in to take over. I believe there are laws in states barring big business involvement at the moment.
Back to black market, it was always easier to get pot than alcohol as a teenager. Pot is considered this heinous gateway drug by relation with the black market. We take pot away from them and lessen their opportunity to expose our youth to worse black market drugs.