Read-Only Friday is a wonderful tradition. It is the day of the week where one avoids making any changes to his or her production environment at all costs. The goal is to prevent having a terrible weekend when a change is made that has unintended (and potentially dire) consequences.
If there are problems, of course they need to be resolved but Read-Only Friday is not a day to roll out updates or bring machines or services down for maintenance. This is all especially true for small businesses like the one I work for that don't budget for redundancy.
It is also a good day to enjoy cheese steaks and non-diet colas.