We recently reported on a 10-year-old child who's required to register as a sex offender for abusing younger boys on an Arizona Army base.

It's hard to imagine that a sex offender registry — a public database run by states — would include anybody who wasn't an adult pedophile or a rapist or seriously dangerous in some way. But sex offender registries can ensnare and publicly humiliate people who haven't victimized anybody at all.

Here are some of the more surprising ways you can end up on a sex offender registry:

1) Taking naked photos of yourself — if you're a minor. Teenagers who take nude photographs of themselves could get charged with child pornography and be put on sex registries, according to a 2013 report from Human Rights Watch. Kids who send naked photos that are viewed in another state could be charged with a federal crime, personal injury lawyer Linda Jane Chalat has written.

A 15-year-old girl in Pennsylvania was charged in 2004 with spreading child porn after taking nude photos of herself and putting them online, according to Human Rights Watch. She was still on the sex offender registry as of 2012.

2) Visiting a prostitute. While former New York governor Eliot Spitzer does not appear to be on New York's sex offender registry, patronizing a prostitute is considered a "registerable offense" in the Empire State. Until recently, some prostitutes in Louisiana could be registered sex offenders, too.

3) Peeing in public. At least 13 states require sex offender registration for public urination, according to Human Rights Watch's comprehensive review of sex offender laws in 2007. Two of those states specify that the urination must happen in front of a minor.

4) Flashing your breasts. You can get arrested for indecent exposure in California if you flash your breasts in front of a lot of people in order to gratify yourself or offend somebody else, according to the Shouse Law Group, a group of California criminal defense lawyers. And indecent exposure can land you on the sex offender registry.

5) Having consensual sex with a teenager, even if you're a teenager, too. At least 29 states require teenagers who have had consensual sex with each other to register as sex offenders, according to the Human Rights Watch Report from 2007. In Georgia, a woman named Wendy Whitaker was on the sex offender registry for years for having sex with a classmate when she was 17 and he was 15.

6) Sleeping with your sister. Incest is not just a social taboo; it's also illegal in a lot of states. Football player Tony Washington learned that lesson the hard way after getting in trouble for having sex with his 15-year-old sister when he was 16. "I didn't know it was illegal," Washington told ESPN in 2010.

Washington, who had an incredibly troubled home life, pleaded guilty to prohibitive sexual conduct, according to the Toronto Star. He was charged under a Texas law that bars sexual contact between family members. He became a registered sex offender. His past continued to haunt him.

7) Giving another child a hug. There's been momentum recently to get rid of requirements that children register as sex offenders, the Wall Street Journal reported. Five residents of Colorado who were found delinquent for sex crimes as kids recently sued the state to fight a law that forced them to register as sex offenders, according to the Journal.

One of those Colorado residents had been accused of trying to hug a girl at his elementary school too much when he was 13.