This bill is funny because it already is legal to own and sell bitcoins. I guess the only difference is that now exchanges will have a foothold to help ensure their security, and of course the price is going to skyrocket when this passes
It actually isn't that uncommon. Since the laws on the books are written over the course of centuries the particular status of something can sometimes been undefined. While no law previously in CA explicitly by name declared Bitcoin illegal, the existing laws of "lawful money" brings up at least the question on if Bitcoin violates those.
A company would much rather have a situation where a law explicitly defines something as lawful then a scenario where it "probably is lawful because nobody has had all their assets seized by the state ... yet". My guess is some business interest in California lobbied to get this passed. Putting something in explicit black and white is always a good thing (well as long as you are favor of what is written).
