I've had my luggage lost twice, but neither time was that big of a deal. They drove it to my home (one case was about 30 miles away, the other was 45 miles away) free of charge as soon as it arrived. Luckily it never happened to be when I was staying in a hotel or something so I always had enough clothes.
1. airlines that don't have individual video entertainment monitors, esp for international flights
2. crying babies. there should be a separate soundproofed section for people traveling with babies.