Why does the leaderboard in Travel-Other-Destinations always change?

The Leaderboards are updated daily. If the 2 people are close to each other in numbers, they may be switching places day-to-day as they each get new Best Answers. The other possibility is that you have bad cache files that you are hitting on some of these. You should clear all your cache files before checking these thiings. Finally, there is the possibility that Yahoo Answers either has a bad cache file on one of the servers, or is having a glitch. They DO happen here. If you feel that is the case, report it as a BUG at the Suggestion Board on the ABOUT tab above the green bar.