Services should log there error causes to syslog. They can do that either via the syslog() libc call or by simply writing to STDOUT/STDERR, and using StandardOuput=syslog in the service file.
In F16 we plan to set StandardOutput=syslog by default. We are currently holding this back in order to support generic syslogs with SysV init scripts where such a default would result in a logging loop.