I have never made anywhere close to being able to be affected by this, nor do I have immediate plans to. I'm a nonprofit entrepreneur, and part of the reason why I am moving out of california is precisely because of crap like this. I think there's a lot of questionable moral anti- and pro- tax arguments (the "no double taxation" argument is one of them, I think - if taxation is okay at any level, why is double taxation any worse).But a retroactive tax offends the morality because as a matter of principle the relationship between the individual and the state should be well-defined at any given time - to engender rational planning on the part of the individual. The only retroactive things that should happen should afford leniency to the individual (for example, commuting sentences). That this has happened, quite frankly, is terrifying on principle and as precedent - even if it does not affect me.
What if california decided to legalize marijuana via the legislature, and an upset populace decided to retroactively make it illegal by referendum in november, and police decided to round up people who had offended the law earlier in the year?
For what it's worth, I voted against prop 30, mostly because I knew that it was retroactive.