In vehicular ad hoc networks (VANETs) tracking of participants is an issue that is examined by many research groups. These groups came up with several different concepts of counter measures against tracking attacks. All of these presented techniques seem to offer a pretty good protection. We pick out two very promising concepts - the Mix Zones and the Silent Periods - to examine them in a simulation environment to actually identify their strengths and weaknesses. Our simulation results show rather high success rates for attackers with relatively unsophisticated attack heuristics. Furthermore we confirm the correlation between several influencing factors and the success rates of attacks and study the connection to the common metrics k-anonymity and entropy.