Location based services (LBS) let people retrieve and share information related to their current position. Examples are Google Latitude or Panoramio. Since LBS share user-related content, location information etc., they put user privacy at risk. Literature has proposed various privacy mechanisms for LBS. However, it is unclear which mechanisms humans really find useful, and how they make use of them. We present a user study that addresses these issues. To obtain realistic results, we have implemented a geotagging application on the web and on GPS cellphones, and our study participants use this application in their daily lives. We test five privacy mechanisms that differ in the awareness, mental effort and degree of informedness required from the users. Among other findings, we have observed that in situations where a single simple mechanism does not meet all privacy needs, people want to use simple and sophisticated mechanisms in combination. Further, individuals are concerned about the privacy of others, even when they do not value privacy for themselves.