Another reason to keep it in your pants (or at the very least, wrap it up): the number of Chlamydia infections hit an all-time high in 2010. A new report from the Centers for Disease Control reveals that an estimated 19 million new STD infections happen every year in the U.S. alone, which means almost one in every 16 people in America have an STD.

Incidences of Chlamydia, or "the Clap," increased the most. In 2010, 1.3 million cases were reported, a 5.1 percent increase from 2009, and the most reports of any medical condition. The CDC credits some of the jump in numbers to expanded screening efforts, but also notes that the majority of infections go undiagnosed, so the numbers are probably more around 3 million. Chlamydia is a bacterial infection that, if untreated, can spread and cause urethritis in men and infertility in women.

While cases of Gonorrhea are declining, the CDC reports that there were 300,000 new cases last year, and even more troubling, it's becoming resistant to the antibiotics used to treat it. Gonorrhea is another infection that can cause infertility in women and, at the worst, meningitis in both men and women.

Syphilis cases decreased by 1.6 percent for the first time in 10 years, but increased drastically among young black men. Syphilis infections cause sores and rashes in its early stages, but can stay latent in the body and cause brain, nerve and organ damage.

Something to consider the next time you're cruising for girls at a bar.