As with all things there must be balance and compromise. If it gets to the point where you spend more money on security than the value of the items stored - people will stop bothering.
The biggest lesson from UO which PFO will need to learn: people do not play a game to be victims.
The easier it is to steal/murder and the more commonplace such actions are the less players you will have. Less players, less victims, less income. Look at the final phase of UO where the anti-pvp servers emerged - they were swamped.
I'm looking forward to PFO coming out but I'd rather put up with a few immersion breaking things than try to play in a ghost town.
