Only within the past decade or so have people been able to communicate instantaneously and at any time, without regard to geographic distance or any of the natural things that used to put restraints on us. For instance, throughout all of Christian history, if a married man started to spend too much time alone with a single woman, everyone in town would talk and the parish priest would privately admonish both of them. Nowadays they can bare their souls to one another via email, and no one is the wiser - and even if they don't bare their bodies via Skype or sexting, they may have crossed a line without completely realizing what they were doing. I've known people who have fallen into this habit almost unawares. It's like taking a very strong drug that no one has yet figured out is addictive.
It's also quite possible - for teens in particular - to develop a tremendously intense and weird intimacy by being always with a friend in a virtual way 24 / 7. I know a teen whose Skype is always on, though the video is sometimes off, and she and her boyfriend who lives 1,000 miles away (and who is not the most well-adjusted of persons) are either constantly listening to one another's lives unfold as they carry their laptops about with them, incessantly texting, instant messaging, or (if it's late), watching each other masturbate. Disturbing as that last bit might be, it pales in comparison to the psychological effects of being a kind of electronic Siamese twin to someone you've never even met in person. Her parents are clueless. They don't for a minute suspect that their daughter's being with this guy non-stop every waking moment - and being with a lot of other bizarre strangers she meets at weird social sites - is bad for her.
And then there's the internet's effect in Catholic circles, where I've noticed two phenomena I think are directly related to the nature of the new technology. First, fringe groups like the Radical Traditionalists are given much more prominence than they actually have. Since the rad trads tend to be readers and writers as well as obsessive compulsive and paranoid, the internet suits them perfectly. The noise they make on Facebook and blogs leads one to believe that the Church is in an utter hateful antisemitic meltdown. They use the hit-and-run nature of the anonymity and pseudo-authority comboxes and blogs provide to make everyone think they're a far greater presence in the Church than the mere one percent or less of the overall Catholic population that they happen to be.
The other odd thing I've noticed is that unbalanced people, or run of the mill "cranks", can cause far more trouble on the internet than they can in newspapers or even talk radio, where comments are by and large edited and screened. I personally know of one Lone Ranger clergyman out there who has been banned from a dozen blogs and elicited scores of complaints to his ordinary for troubling people in a way that he would never be able to get away with in the days of the old technology - newspapers, television, talk radio, postal mail, telephones, etc. The immediacy of internet communication, the small amount of effort required to press a point compulsively, the lack of editorial oversight, the ability to use the internet to focus on any subject or person that interests you without limit day and night, and the appearance to readers that everything asserted on the internet by someone who has a kind of authority and who writes with conviction must carry a certain veracity (this is a holdover from the days when it took a certain real authority to become a published author) - all of these factors combine to allow both fringe groups as well as fringe individuals an environment in which to flourish: the way a warm day will allow a bacterial culture on your picnic lunch to flourish.
And, as usual, Cracked has a lot of insight on this subject.
People like to be terrible, and the Net makes it easier to be terrible. It lets them put their cruelty out into the world without the burden of being tethered to it. They are released, and they sprint happily across the World Wide Web dropping little nuggets of awful without consequence. ... Has the Net made people more awful? Impossible. That's like drawing horns on a picture of Hitler -- doesn't add a lot. But the Net is a tool for the awful who already exist. And it provides a safe haven where they sharpen their cyber-weapons in the dark.