According to a 2010 report by the Centers for Disease Control, noncontact, unwanted sexual experiences were the most common form of sexual violence experienced by women. One-third of women will experience this type of sexual violence in their lifetime, compared with 12.8% of men.

May wanted to take all the stories she heard from friends and colleagues and do something useful with them. There isn't a lot of data out there on street harassment, and she is hoping that Hollaback! can change that. For her, the motivation is simple: "This is a human rights issue. This infringes our right to walk down the street safely, and we pay taxes too, we deserve to walk down the street and feel safe."

Why catcall at all?

On the streets of Atlanta, men offered varying opinions about what motivates street harassment, whether they partake in it or not.

Kareem Watkins, a 26-year-old insurance claims adjustor said: "A lot of times it's like pressure amongst men to like, you know, put on a show in front of each other. And kinda humiliate women sometimes ... We're raised to objectify women because we live in a TV world."

But, Watkins went on to say that some women might be flattered by the attention: "I have heard that when a guy walks by a girl and doesn't look, that she's hurt by that," he said. "I imagine it might feel pretty bad, but you know I can imagine it might boost their ego."

Watkins and his friend Jay Woods also put the onus on women for inviting commentary with their style of dress. "Did her mom tell her how to wear that? It's all about how you're raised," said Woods.

And while neither of them could explain how a woman might command more respect while walking down the street, both did agree: "Women get treated the way they allow themselves to get treated."

But for Marcus Jeffries, a 25-year-old student, catcalling is more about biology: "Men prey on women, unfortunately, because women [have] things that men want." His friend Tyrone Evans said it "makes you look like a pervert ... like [you've] never seen a woman before."

Jared Ripps, 39, says he's never even considered catcalling a woman. Why? "I have a sister and I wouldn't want people doing that to her," he said.

It happens every day

According to a survey that Cornell University conducted with Hollaback! in New York City, 60% of reported incidents of sexual harassment happened on the street. A further 22% happened on public transportation or in terminals.

Lt. Stubkjaer of the San Diego Sheriff's Department recommended that in order to prevent harassment, women might choose to walk with a friend or in groups, and practice "basic personal safety protocols." But some women would argue that they should be able to travel independently.

Lola Binkerd was on a train in Los Angeles last month ago when she was sexually harassed. After already switching cars to avoid a group of young men who'd started verbally haranguing her, Lola found herself in a virtually empty car, save for a man with a bicycle.

"He sits down in the seat across from me he leans in and tries to be very flirtatious and I look him in the eye and I say, 'Please leave me alone'... very quickly he became very angry, very agitated ... and then he stood up, punching walls, and it escalated to him shouting sexual threats and threatening to shoot me," she says.

Like Gilbert, Binkerd also blogged about her experience. Her story revealed another aspect of sexual harassment: "There's this expectation that you can't just tell them to leave. People tend to think of it as 'it's not a big deal, just be nice.' They don't realize that someone's making you uncomfortable. ... The idea that you have to be nice when someone is invading your space is ridiculous," she says.

The women CNN spoke to who blogged about their experiences aren't looking for pity, they said, they're looking for awareness.

Holly Kearl, founder of the website Stop Street Harassment, said she believes sharing stories is a key to ending street harassment. The site collects instances of street harassment and maps them.

"We can read other people's stories and see that we are not alone, we can find ideas for standing up to harassers," she said in an e-mail to CNN.

Kearl sees the issue as a global problem that demands more attention, and while street harassment has historically been seen as normal, it is now "less so than before because so many people are speaking out, exposing just how often it happens ... and the negative impact it has on our lives."