Just this very morning, we were teasing an officemate (Ms. X) who left her phone at home. Ms. X's father sent a message to her friend, notifying her of Ms. X's forgetfulness and jokingly ending with "Her secrets are now open to me. Hehehe."

I doubt if Ms. X's father would really look through her phone. But the fact remains that Ms. X is lucky she left her mobile at home, in the possession of people she trusts. What would happen if she left it behind in a public place, where any stranger can claim it for themselves?

A smartphone or PDA is a gold mine of secrets. Even if you really have nothing to hide, the numbers on your gadget may contain information thieves can use to defraud you. At least one friend keeps his social security, tax information, and bank account numbers on his phone. And, at least in the US, you can go very far impersonating someone else if you know their social security number.

And what if you do have something to hide? As mentioned a while back, a local beauty queen was humiliated when pictures of her having sex with her boyfriend made the tabloids (with the naughty parts censored of course). They took pictures of each other during the act with the woman's smartphone, which got snatched. Apparently, the thief freely passed the images around via Bluetooth, and they spread like wildfire.

In any case, the data on your smartphone or PDA represents a big vulnerability. Even innocuous information like your friends' numbers can be exploited. So keep in mind that part of the responsibility of owning a smartphone or PDA-aside from protecting your considerable financial investment-is to keep the data on it safe. Which means taking steps to avoid losing it.

Check out this guide to smartphone and PDA security.