You may have trouble accepting this from some 39-year-old balding bloke who's sitting at a computer in tracksuit bottoms and with chocolate smeared around his mouth, but here goes, regardless: sexual flirtation isn't what it used to be. In a more innocent age a nervous smile, or perhaps the fluttering of a fan, may have represented a scandalous invitation to share a carriage while it rolled gently through Vauxhall Pleasure Gardens. But for today's technology-savvy smooth operator, this represents a monumental waste of time and effort that can be circumvented by taking a picture of your genitals and beaming it over to someone's phone, accompanied by a note along the lines of "Hi, here are my genitals, hope you like them."

"No," wails a nation of people that are still keen to consider themselves capable of romantic behaviour. "This cannot possibly be true," they continue, plaintively, before firing off a text to the person they recently exchanged nude pictures with, urgently requesting that they dispose of the evidence.

The collective gasp of disbelief directed at New York congressman Anthony Weiner (pictured), following his accidental slip-up that caused him to post a picture of his bulging underpants to thousands of Twitter followers rather than the woman it was intended for, stands in contrast to data collected by Michelle Drouin, a professor of psychology at Indiana University.

According to her survey, lewd pictures and videos are exchanged by 60 per cent of people in a committed relationship and 50 per cent of those involved in a fling; while her data obviously doesn't cover politicians who flirt online with people they've never met, there's little doubt that the general practice is more widespread than media reports would have us believe.

Why do we do it? (I use the term "we" rather loosely; my own attempts at online flirtation steer well clear of exchanging lewd pictures, and consist more of paying repeated compliments while desperately playing the sympathy card in the hope someone will take pity on me.) Well, it's facilitated by an era of astonishing contactability; from the rekindling of old flames via Friends Reunited to eye-popping adult hook-up sites, a sizeable chunk of the web seems devoted to facilitating sexual liaisons. After all, whatever our moral guardians might say, we're predisposed to sexual attraction. And sharing pictures and videos has become second nature; naughty Polaroids are the thing of the past and digitally immortalised pictures of boobs and balls are the future. Chat Roulette was the most searched for term on the internet last year, partly because of mainstream media coverage, partly because it was an unusual way to meet strangers, but mainly because of the fact that nakedness was rampant.

Weiner was an idiot, of course. He's married, he was hoping to run for the New York mayoralty, and further revelations about his other online indiscretions demonstrate questionable judgment to say the least. While some encounters came under the "mutual consent" banner, some evidently didn't. And whether online or offline, unwanted sexual advances surely constitute sexual harassment. But even if "sexting" (I've tried my best not to use that word, apologies) is mutual, there are still innumerable reasons to resist that excitable impulse – not least because an overwhelming feeling of shame and regret will surely engulf you afterwards. Ideally, photo recognition software would identify lewd pictures as you attempt to send them, and present you with a series of dialogue boxes to click through - "Are you sure?" "Really?" "You know what's in this picture, right?"

While studies have determined that older "sexters" tend to be driven by power and dominance, for those in their 20s and below there are no such associations; it's just normal behaviour. Much has been written about its worrying spread to those in their early teens, but it seems unstoppable.

Apple patented a message screening system a couple of years ago (still not deployed) that was perhaps designed to combat it – although Apple's example stated, somewhat innocently, that it "might require that a certain number of Spanish words per day be included in emails for a child learning Spanish"). Ha. Sexual impulses will always be stronger than filters, but romance... is there an app for that yet?