These days you don't even need to be assaulted to have your money stolen at an ATM. I have been alerted to a scam that's been going on, called skimming, which involves someone placing a card reading device on top of the front panel of the ATM machine which records your card information when you insert it. A hidden camera, often disguised as a deposit envelope holder, records your password as you enter it.
Thieves will take this information, create an bank card with your recorded information on it, and use it to empty your account and the hundreds of others that have been compromised.
The photos I saw of a skimmer were found on an ATM machine in Mexico, at a Mexican bank. The tip off is to see where a panel is not firmly attached or actually a part of the main front panel of the ATM. I looks like an additional unit of top of what should be a smooth surface.
To read a good article on this, check
http://www.bankrate.com/brm/news/atm/20021004a.asp
As always, if someone smells fishy it usually is.