5) I agree with what he's saying. He's not saying thats its good, but saying its not as big of a deal as what post people make it out to be. Yes root is disabled through 'ssh', which is good why enable it. But I have a tendency to do a sudo tcsh soon as I log in thus becoming root.
4) I'm not getting into the argument, but also keep in mind as root you can do a su - pgsql (or any other account) as become that user as well.
3) *nix get viruses the same way windows do. Somewhere there is a hole and something exploits. I'm not sure the difference between worms/viruses but I remember a few years back solaris had that massive hole in telnet which they created a worm out of which would compromise other boxes.
2) See above #3.
1) We typically reboot our machines on regular basis (usually once a week). I know as a solaris admin a lot of patches require single user mode to install (usually cluster patches). As someone else stated, If you reboot once in a while you become more confident that the machine will actually come back up. I've seen where sysadmins won't patch machines because they are so afraid of rebooting the machines. So like the other user stated, on those times where you have a hardware failure and need to take the machine down for whatever reason, I'm much more confident that it will come back up because it gets rebooted a few days ago opposed to if it hasn't been rebooted in 5 years.