Volatility is definitely an issue, but since it's an online currency, in practice most people will just set their prices in regular currencies and convert automatically when you pay. I've got some money server code that does this for OpenSim - it's not rocket science. That means your customers have some unpredictability in the value of the balance they hold, but as you say nobody should be putting more money into Bitcoins than they can afford to lose.
On crime - well, just like you say, Bitcoins are a lot like cash. Don't hold large amounts of cash unless you know what you're doing.