My key fob stopped working for no apparent reason. I have 30,000 miles on a 2008 so it was covered by the warranty. Very fortunate because a new fob is $250 and programming is $150. The key is fun but not so much for $400 and huge headache if you are far from home and no dealer is close by to rescue you.
Better carry a cheap spare for travel. See my post #4 here: http://priuschat.com/forums/gen-ii-prius-main-forum/81961-nowhere-put-backup-smart-key-clicker.html
