Manhattan-based company STFree Certifications provides its health-conscious customers a sexual history "license" with a phone number on the back that enables them to prove their testing backgrounds to potential partners.

More than 15,000 people nationwide have signed up for the STFree service, launched in 2004 by Bedford-Stuyvesant, Brooklyn, native Eli Dancy.

Dancy, a former club promoter, said he saw "a lot of irresponsibility" in his neighborhood and created the STFree card to help raise awareness.

"In places like where I grew up and where I worked, there are incredibly high HIV and STD rates," said Dancy, 28. "This card opens up the conversation for people to talk about it."

The latest research, published in the Journal of Sexual Medicine, was carried out the Dr Emmanuele Jannini at the University of L'Aquila, and involved just 20 women.

Ultrasound was used to measure the size and shape of the tissue beyond the "front" wall of the vagina, often suggested as the location of the G spot.

In the nine women who reported being able to achieve vaginal orgasm, the tissues between the vagina and the urethra - which carries urine out of the body - were on average thicker than in the 11 women who could not reach orgasm this way.

However, Dr Tim Spector, from St Thomas' Hospital in London, told New Scientist that the thicker tissue might actually be part of the clitoris - another extremely sensitive area.

Another suggestion was that, rather than being the cause of more orgasms, having these frequently might actually lead to better-developed musculature in this area.

More than a quarter of respondents -- or 28 percent -- admitted spending less time socializing face-to-face with peers because of the amount of time they spend online.

It also found that 20 percent said they spend less time having sex because they are online.

Cell phones won out over television in a question asking which device people couldn't go without but the Internet trumped all, regarded as the most necessary.

"It is taking away from offline activities, among them having sex, socializing face-to-face, watching TV and reading newspapers and magazines. It cuts into that share," said Mack.

"I don't suppose their partners are too pleased about it."

Mack said a clear trend to emerge from the survey was the increasing need for mobility with people no longer satisfied with just broadband access from home and wanting hand-held devices like iPhones and BlackBerrys.

Physical reasons such as to reduce stress ("It seemed like good exercise"), feel pleasure ("It's exciting"), improve or expand experiences ("I was curious about sex"), and the physical desirability of their partner ("The person was a good dancer").

Goal-based reasons, including utilitarian or practical considerations ("I wanted to have a baby"), social status ("I wanted to be popular") and revenge ("I wanted to give someone else a sexually transmitted disease").

Emotional reasons such as love and commitment ("I wanted to feel connected") and expression ("I wanted to say 'thank you'").

Insecurity-based reasons, including self-esteem ("I wanted the attention"), a feeling of duty or pressure ("My partner kept insisting") and to guard a mate ("I wanted to keep my partner from straying").

In a survey of 1,000 British adults by car hire firm Holiday Autos 58 per cent of Brits admitted getting it on in their motors, with the flipped passenger seat position the most popular.

Four percent of US adults have never had sex in their lives, and the figure climbs to 12 percent in the case of Mexican-Americans, according to an official survey out on Friday.

"Approximately 96 percent of adults age 20-59 years have had sex, with the age group 20-29 having the lowest percent (91 percent)," the Center for Disease Control and Prevention (CDC) said in a report.

Eighty-eight percent of Mexican-American adults have had sex, a lower percentage than any other ethnic group.

The report also said 16 percent of adults first had sex before the age of 15, while 15 percent abstained from sex until age 21 or older.

For that, Laura Sessions Stepp, author of "Unhooked," and a writer for The Washington Post, has been criticized as a throwback to an earlier, restrictive moral climate, an anti-feminist and a tut-tutting mother telling girls not to give the milk away when nobody's bought the cow.

The author "imagines the female body as a thing that can be tarnished by too much use," wrote reviewer Kathy Dobie in Stepp's own paper, the Post, and suggested that Stepp was, in one part, trying to "instill sexual shame." For Meghan O'Rourke, literary editor at Slate.com, Stepp is "buying into alarmism about women," and making sex "a bigger, scarier, and more dangerous thing than it already is."

Stepp argues these critics have misconstrued her ideas.

True, she regrets that "dating has gone completely by the boards." replaced by group outings that lead to casual encounters. True, she regrets that oral sex "isn't even considered sex anymore." But she isn't saying girls should not have sex; just that they should have it in the context of a meaningful connection: "I am saying that girls should have choices."

Too often, Stepp argues, girls and young women say proudly that they like the control "hookups" give them - control over their emotions, their schedules, and freedom to focus on things like schoolwork and career (the students she profiles in her book are high achievers).