However, back in good old days, I've found few bugs, which I didn't post, for various reasons, mainly because most of them were not very serious, or I wanted to do some studying before posting. I think I'd better share this with Bugtraq community while I still remember it. Unfortunately, I don't have root access to 5.3 anymore, so some descriptions may be not totally accurate where it comes to 5.3, I apologize for that. So it's pretty much like suid shell sitting around, in case you forget root password. It does all kinds of other dangerous stuff as well, e.g. predictable tmp files.
Obvious fix is to strip suid bit, which is most likely to break it.
I don't know why it's necessary to be root to establish non-authentificated connection between two machines, but I guess SGI guys know better. It doesn't protect you from all evils, notably nothing can be done about tmp files, but it's better than nothing. It's a pretty bad one. It allows anyone to get lp priorities. Even if you wisely strip suid bit off lpd, it doesn't help a lot, hacker can still steal identities of people who print.