At first I found the bash figure puzzling too, but that's probably because I've been around long enough and used enough different *nix OSs that I think of bash as just one of many shells. But for many people whose only *nix experience has been on Linux, "bash" is synonymous with "shell," so I assume many of those selecting bash really meant "shell scripting."

Looked at that way, I do think a certain amount of shell scripting is very useful. I've gotten a lot of productivity out of "for i in *; do something; done" and other basic shell constructs over the years. I'd hate to have to do any serious programming in shell, though. One time I tried to work on a fairly complex bash program (I was trying to port it from Linux to FreeBSD, and if you're wondering why a shell script would need porting, so was I), and it was painful.

I suppose another way to put it would be to say that shell scripting is a critical skill for system administration, but not for much else. A sysadmin might be able to get away with not knowing Perl, but he needs to know shell. On the other hand, Perl is useful for almost anything, but not required for any particular task.

Python is right out.