The Surgeon General Warns: You're Not Just Reading That Book, But Also Every Other Book That That Person Has Ever Read

Tuberculosis, smallpox, SARS, and the common cold are all possible side effects of bookcrossing -- a hip, new, media-invented trend wherein folks leave their recently read books lying about as gifts for like-minded strangers. Tech geeks (this means YOU, dear reader) can even register their books online and then track their journeys from reader to reader, city to city, country to country. (Or you can always just check the Center for Disease Control for recent outbreaks stemming from your region.)