As many people have pointed out, the languages that are described as unfit for business use aren't always. In particular, just as I've written ten-line perl scripts to do what would have taken 40 lines of (unreadable) C, I've written 10-line Prolog programs that did what would have taken 100 lines of Perl. And yes, I get paid. You said that it's good for AI - well, it's good for lots of other things. I haven't had the chance to code them myself, sadly, but what do you think phone switch controllers are written and debugged in these days? You betcha - Prolog (at least, according to my prof who was teaching us Prolog at the time). And their codebases are HUGE.

Just my dime/5.