I pulled this statistic from teh interwibz:

Looks like 4 companies in the United States account for 92% of cigarettes sales.

If I'm not mistaken, back in the early 1900s there were far more tobacco companies in existence.  Competition drove a lot of them to consolidate with buyouts or drove the lesser companies into bankruptcy.  That's my recollection based on something I read a while back, and it could be accurate.  However, my point is that only a few tobacco firms survived and thrived.
 
In the early days of a new industry, there emerges an abundance of new companies trying to capitalize on the new technology.  It happened with railroads, cars, internet stocks, and more.  Keep in mind that very few survive and eventually become profitable.  I think this new marijuana stock trend is just like all those other examples I mentioned--while you might be able to make good money by day trading them, I think it's foolish to go long on any of them until they concoct a solid plan to become and remain profitable.