When CA promised that raising cigarette taxes would help ballance the budget, everyone with 1/2 a brain said it wouldn’t work.
The only thing taxing pot in CA will do is turn I-5 into the Pot Transport Coridor of the USA w trucks moving Pot into the state and $$$ to WA, OR and Mex.
If you raise taxes then black market sales and those people quitting because of it will of course mean total revenue will not go up.
I don't like pot, but the practical sides of this are plentiful. You'll get savings of law enforcement $$$ because one main gang income is removed. Jails will get less crowded, allowing for more violent criminals. Price will go down due plentiful supply and lack of criminal-related overhead, so use will likely not go down as with cigarettes. All this means the net balance for the state's books is likely to be quite beneficial as long as the tax is not at such a level as to recreate a black market (if legal, taxed pot is more expensive than criminal-supplied pot, then economics says people will buy the criminal stuff).
My big reservation has been mentioned, how do you scientifically tell if someone's stoned? We need that to be able to bust stoned drivers just like we do drunk ones. We also need to make sure that although pot would be legal, employers would retain the right to fire or refuse employment to pot heads. I sure wouldn't hire one.