Backrub chains appear frequently at youth groups and bible camps. Whenever pubescent* Christians of mixed gender are gathered to study the Bible or worship, the likelihood that a backrub chain will form is increased tenfold.
Backrub chains do not appear nearly as often in non-Christian settings. This may be because there is more frustration present in people who “struggle” with kissing, etc. before marriage. In the evangelical subculture, mass backrubs in an open setting are considered acceptable.
*The presence of backrub chains can extend well past adolescence, into singles ministries and, creepily, beyond.