Services which may be enabled by Default
If a service does not require configuration to be functional and does not listen on a network socket, it may be enabled by default (but is not required to do so).
In addition, any service which does not remain persistent on the system (aka, it "runs once then goes away"), does not listen to incoming connections during initialization, and does not require configuration to be functional may be enabled by default (but is not required to do so). Examples of "runs once then goes away" services include iptables and udev.
Finally, there are some services which are permitted to be enabled by default as specific exceptions:
All other services must not be enabled by default. If you think that your package contains a service that should be enabled by default, but does not meet the above criteria, you may request an exception from the FESCo.