That data is incredibly revealing and potentially damaging.
Andrew Auernheimer, a controversial computer hacker who looked through the files, used Twitter to publicly identify Adult Friend Finder customers, including a Washington police academy commander, an FAA employee, a California state tax worker and a naval intelligence officer who supposedly tried to cheat on his wife.
Adult dating or no-strings-attached dating is a variant of a traditional online dating service.
The information exposed can be particularly devastating to people living in small towns, where they are more easily identified.
For example, one person exposed in the hack is a 40-year old welder from a small Illinois town of a few thousand people.
Many adult dating sites focus on the local aspect of finding a match.
Some users regard the service as no different from finding a one-night stand on a night out.
All Paid users can message and post and they also have added benefits.