I was digging through my purse earlier this week and ran across a small white card with a black magnetic strip. After puzzling over its origin for a few minutes, I remembered that it was the nondescript key to an equally nondescript hotel room where I recently stayed on a business trip. I tossed the card in the trash, but thankfully light-fingered tourists from earlier times decided to keep their keys as souvenirs, thus spawning one of the more popular categories of hotel collectibles.