When you ask someone to name a friend of theirs, the person they name is almost always more popular than themselves. It's called the friendship paradox. But the cool kids with thousands of Facebook friends may find a major downside to their popularity. They're likely to get sick far quicker in an epidemic. During the 2009 flu season, researchers at Harvard compared a random sampling 319 students to 425 of their more popular friends, and the latter group got sick two weeks before the control, and a whopping 46 days before the epidemic peaked.
While this research can be used to spot epidemics before they go big, I know what it really means: When the zombie apocalypse comes, the people with the highest Facebook friend count will be the first to turn.
Read the research paper about this in PLoS One