Legal Question in Banking Law in California

Why do I think there is more to this story. You have a moral obligation, and possibly a legal obligation, to give back the money. Don't spend it: the same dumb corporation that electronically deposited money in your account is equally capable of withdrawing it again, leaving you with an overdraft. That said, if you leave the money in your account and no claim is made within three years it's yours.

I guess that depends on who deposited it and why.