On Saturday afternoon, an apartment complex just a few blocks from Colorado State University in Fort Collins hosted its annual pool party for students. Within hours, thousands of people showed up, at least 10 people were taken to the hospital, and four people were arrested in connection with a fight, including two football players, according to the Rocky Mountain Collegian student newspaper.

How did many people hear about this annual party? From a Facebook invite that received nearly 3,000 RSVPs. (Police told local media outlets that at least that many people showed up.)

Is it even possible to fit thousands of people in one apartment-complex-size pool? Uh, no. (If you watch videos from the party, you can barely see the pool through the mob of bikini-clad women and shirtless guys.)

We live in an amazing time when sites such as Facebook and Twitter instantly bring us news of earthquakes, hurricanes and random things fake people said. At the same time, social networking without bounds can instantly expand your guest list beyond friends-of-friends you can trust to friends-of-friends-of-friends who don’t feel bad if they drink all of your beer, break your stuff, hit on your significant other, start fights and attract the cops.

This isn’t the first time that social media has made parties dangerously social. In June, a teenage girl in Germany had more than 15,000 people confirm to attend her birthday party via a public Facebook invite, and 1,500 people showed up. In April 2010, a block party near James Madison University attracted thousands via Facebook and text message, and was then shut down by police in riot gear.

And what do you do if a Facebook-promoted party gets out of hand? The Collegian editorial staff offered up this advice: “When you arrive at a party and see that stuff is going downhill, leave. Don’t contribute to the disaster area.”

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