You take precautions with your data and that should extend to the information you store on your smartphone using a microSD card.
It's fast and easy to activate the encryption function in Windows Mobile, for example. This should prevent any other phone from being able to see the files on your storage card.
Here's how to do it:
From the Start Menu, choose Settings, then click the System Tab. Check the "encrypt files when placed on a storage card" box. (On some devices, Encryption may come up as an option when you choose Settings.)
Note that if you ever reset your phone to the factory defaults, you will no longer have access to those encrypted files (so you may want to make a habit of backing-up your memory card onto your computer or some other device).
Remember that when you have encryption turned on the files on *any* storage card will be encrypted. So, if you're going to pop in someone else's card, for example, turn off the encryption option before inserting it so that the person who gets it back and still use it.
