Fisking mode on, devils-advocate-to-some-extent option engaged.
I think that the world of TV, computers, video games has caused us to lose our connection with the physical world. Add on top of that fear: fear of letting children play in the street, fear of chemistry sets, fear of ultraviolet light. This combination means that people (and especially the young) spend hours indoors away from the physical world immersed in virtual worlds.
In my experience (and I'm only talking about my own experience), the fear is driven by "predators". People aren't significantly more worried by actual dirt than they used to be — kids in my neighborhood are filthy often. But there's a perception that there are dirty perverts behind every corner ready to snatch your kid from you — it's not so much of just a concern as much as a near-certainty. This is driven by "news" shows that focus on the handful of negative events out of the billions of positive ones - in other words, it doesn't at all reflect the reality than one sees in statistics. But, many people aren't statistically minded. Some kids are definitely losing out because of this. All we can do is allow our own kids the reasonable freedom that they're entitled to… I see many people doing so.
Books: as books move to electronic form they take on a different meaning. The words of the book transcend and the physical presentation is lost. On the Kindle every book is Twilight. In the real world the physical book has a meaning of its own: it's the book your wife gave you as an anniversary present, it's the book your late father got part way through and you dare not remove the bookmark he left in place, it's the children's book read and read until the pages are torn and worn. These physical remnants augment the book with personal meaning.
Speak for your own ebook reader - mine isn't filled with Twilight. Are more people buying Twilight than deep eternal classical philosophical works? No doubt, but that's not at all necessarily related to medium.
Sex: what happens when pornography becomes the default means of getting sexual pleasure. Does fantasy start to wither in the brain? If every fetish or desire is available (for free) at the touch of a button what happens when we are presented with a real other person to have sex with. And what's the cost of reality not matching screen fantasy?
Masturbation has always been the default means of getting sexual pleasure. It's assisted more now and I agree that's something to be cognizant of. But I remember wails a few years back of how rape was skyrocketing as corner convenience stores started selling pornography. I don't have the numbers in front of me, but my understanding is that rape, like most violent crime, is decreasing and is (in developed countries) at pretty low levels historically.
While we're theorizing, we could speculate that many peoples' sex lives are better now: as (widely-desired) taboos are normalized, more people get to engage in them. How many married couples have gone through life both wanting and desiring "more" (more pleasure, more intimacy, more "dirty", etc) but neither getting it because they both considered it off-limits? I've known far more couples whose sex lives have been improved by watching porn together than the opposite.
Making: as a child I had Lego, Play-Doh, and other toys to occupy my hands. Now imagine that these are all virtualized and I play with them on screen. There's no difference felt in my hands between them. No texture, smell and pliability of Play-Doh, no satisfying click of Lego, no hunt for the right coloured piece. If an infinite amount of virtual stuff is available does my imagination atrophy? If I can always find the right coloured, right sized Lego piece is this an advantage or a loss because I'm no longer forced to invent?
If you ever build a technological thing that makes kids not play with Lego and Play-Doh, it'll be because it's so immersive, fun, and imagination-stimulating that they don't want Lego and Play-Doh anymore. Every kid I see is surrounded by technology but still loves playing with these physical things too.
Children: as an adult man I'm now viewed by many to be a threat children. I can't be seated next to a child flying alone on a flight. I'm afraid to talk to a child in the street, and we've seen schools instituting policies against any sort of physical contact between children and teachers.
I agree: this is a huge problem. It doesn't seem, though, to be driven by technology but by its offshoot, media. I don't know what the answer is here. As above, I guess it's about making people statistically-driven rather than anecdote-driven. Good luck with that. Horror is more exciting than mundane news about the world being OK. As long as you have a free media, you're going to have this problem. Only possible remedy I see is a heavy educational emphasis on making statistically-based decisions.