Casey Chan an editor for Gizmodo writes "Stealing ATM PIN Numbers Using a Thermal Camera Is Too Freaking Easy"
Andrew a.k.a. Modem Sniffer found a great article explaining how a thermal camera can be used to steal ATM numbers.
Criminals will attach camera to ATM or video you as you use machines, please check around the ATM prior to use for hidden cameras.
Note, these cameras appear to start in price at around 2000 USD, and to avoid is easy by choosing a machine with steal keys.