In our desire to support ever-changing business models, learn from past behavior and provide the best experience for every individual visitor, we are tempted to record as much data as possible. At the same time hackers are more ferocious than ever, with one spectacular security breach after another, and we now know of unprecedented mass-surveillance by government agencies. The term Datensparsamkeit is taken from German privacy legislation and describes the idea to only store as much personal information as is absolutely required for the business or applicable laws. Some examples are instead of storing a customer's full IP address in access logs, just using the first two or three octets and instead of logging transit journeys with a username using an anonymous token. If you never store the information, you do not need to worry about someone stealing it.