Got this in a chain email, and while it may not be true its probably great practice:

This lady has changed her habit of how she lists her names on her mobile phone after her handbag was stolen. Her handbag, which contained her cell phone, credit card, wallet...etc....was stolen. 20 minutes later when she
called her hubby, from a pay phone telling him what had happened, hubby says "I've just received your text asking about our Pin number and I've replied a
little while ago."

When they rushed down to the bank, the bank staff told them all the money was already withdrawn. The thief had actually used the stolen cell phone to text "hubby" in the contact list and got hold of the pin number. Within 20 minutes he had withdrawn all the money from their bank account.

Moral of the lesson: Do not disclose the r elationship between you and the
people in your contact list. Avoid using names like Home, Honey, Hubby ,
Sweetheart, Dad, Mom, etc....... And very importantly, when sensitive info
is being asked thru texts, CONFIRM by calling back. Also, when you're being texted by friends or family to meet them somewhere, be sure to call back to confirm that the message came from them. If you don't reach them, be very careful about going places to meet "family and friends" who text you.

The story is likely exaggerated (if true at all), since unless the couple had a very small bank account, it probably exceeded the bank's daily ATM withdrawal limit.

Really all people need to do is treat requests for sensitive information (like a PIN) with appropriate caution and skepticism.

I think if you'd send something like that in a single, clear-text message, it's really only a matter of time till something like that happens to you anyway.