The use of fieldbuses combined with intelligent sensors and actuators are opening up new possibilities for building control systems. Due to a reduction and a simplification of wire, they can reduce the cost of systems, which own a relatively great number of instruments, and which therefore offer a wide range of possibilities of task distribution, redundancy and reconfiguration. If fieldbuses seem to be a good solution to improve the dependability, it could be also a trap due to the new possible failures they may introduced. In the paper, these failures and their effects on dependability parameters are studied. Some elements are presented in order to provide designers with means to assess dependability at each design step by integrating field feedback. Assessing dependability is too often limited to an evaluation at the end of the design process, which often involves reselecting previous choices. To sum up, this contribution constitutes a structured overview of fieldbus faults given to help users to select the most suitable fieldbus for their applications, both in control and measurement.