So, how did that -l get in.
On FreeBSD, the natd program will log all the aliasing it does when you pass in the -l flag. This log is written to /var/log/alias.log, and is supposed to be truncated whenever natd restarts. So what happens when you start, say, a home gateway server and then leave it running forever like you should be able to do with a Unix box? Well, after a few months, /var/log/alias.log is on the order of a gigabyte, and, of course, it won't go away because natd is running.
When you discover this and are tempted to just kill and restart natd, be sure you don't do it from the outside world, because natd sticks itself to the outside interface of the box and when you kill it, the box goes and blows away the connection you just entered the kill command from.
When I get home, I'll restart natd without the -l flag.