mac geekery

Answer

Well, for starters, it’s not on by default. You had to have turned it on (or some software did) for it to even be active. That said, the service tool can turn it off.

$ sudo service finger stop

The tool can also control any launchd or inetd service:

$ sudo service --list
smtp
fax-receive
bootps
com.apple.KernelEventAgent
com.apple.atrun
com.apple.dashboard.advisory.fetch
com.apple.dnbobserver
com.apple.dnbvolunteer
com.apple.mDNSResponder
com.apple.nibindd
com.apple.periodic-daily
com.apple.periodic-monthly
com.apple.periodic-weekly
com.apple.portmap
com.apple.syslogd
com.apple.xgridagentd
com.apple.xgridcontrollerd
com.vix.cron
comsat
distccd
eppc
exec
finger
ftp
login
nmbd
ntalk
org.isc.named
org.postfix.master
org.xinetd.xinetd
printer
shell
smbd
ssh
swat
telnet
tftp