I study an AI course and we done some lectures about first order logic and the first thing that I was thinking is, what are the real world applications of first order logic and generally logical languages , especially in AI ?
If you want a specific example, IBM Watson should qualify. Check the links for details on how they use Prolog. I'd say that Prolog made a huge hype in its day, and most real today's system are based on different principles rather than "first-order logic programming" in narrow sense. However, there is definitely a niche for this approach. We live in the age of other hypes, that's it.