Direct analysis of failures from the field of application is an effective practice to understand the actual dependability behavior of an operational system. However, despite its wide use over the last four decades on a large variety of systems, field data analysis has rarely been applied to wireless networks. Users accessing the Internet ubiquitously through these networks are increasing, and they expect the same dependability level they already experience on wired networks. But how can we analyze the dependability level of a wireless network? The article defines a novel combined approach to model and analyze the dependability of short range wireless technologies exploiting field data. Through the experience gained from extensive failure analysis of Bluetooth networks, the paper shows how field failure data can play a key role to fill the gap on understanding the dependability behavior of wireless networks.