This is a response to a worried mom of an eight year old.
I'm coming into the discussion a wee bit late and have skimmed the majority of responses and have just a few points to add:
Jane McGonical was on TED Talks. You can view here.
The original poster states a few concerns I'd like to address:
"but I miss my cheerful son who in younger years would happily be up for all kinds of adventures."
"if we do go out, a hour or 2 later he's ready to go home."
"I hate to make an arbitrary ban/regulation of this, but it seems like it might be helpful."
We started 'homeschooling when my son was 7yo and moved into full blown radical unschooling by the time he was 8yo. He is now 14 so I've run the gambit of much of what you address in your questions and this is what I have learned.
1) You haven't really 'lost' your cheerful son. He has grown and his interests have grown with him. Ask him what sorts of adventures he'd like.
When my son was 8, I pulled up the Dwarf Fortress website and let him read it to see if he would like that sort of game. (Got the link off the homeschooling Mensa site so I had no clue how my son would take to it.) He liked what he read and is still actively involved with the game/forum/linked branches/etc ever since. To this day if you looked at what he is reading on his iPod, it's usually something linked from this original site.
Do I worry? Not at all! What I have done is stay connected and in tune with what has him so intrigued. I take the time to listen and get engaged with him and his interests. This also gives him someone close that he can talk to about all his discoveries. It has allowed him to ask crazy questions like, 'Can a carp really kill a man?' which lead to us researching everything about carps and how big they grow, the probability of 'man killing carps' and a game designers right to be as silly as they so choose to be.
Along with Dwarf Fortress, I, who was NOT a gamer in any sense of the word, learned to play Runescape, World of Warcraft, and tons of other 'addicting' games. But my learning wasn't limited to just learning games! No! By bringing my boy home from school, I was now his number one person to whom he spent the most time with. I'm the one he talked to about EVERYTHING. This meant I got to enter his world and I considered it my place to know his interests and feed them. I read all the books he read (and he reads a lot!) so he always had someone to discuss the stories and plot lines with.
When his interests expanded beyond my time constraints/desires/and or tolerance, (I got motion sickness from some of the xbox games) my spouse jumped in. The two of them watched every Star Trek, played Halo, and discussed all types of weighty subjects even doing the math to see if the directors got it right. This lead to them getting into Carl Sagan and Stephen Hawkings to name a few.
My point being is your 'happy son' is still there. You might just need to get to know him again as a slightly older child with slightly grown interests.
2) My son also grew to hating to leave the house. To the point at one point, I feared he would become a shut in. He balked at having to even accompany us to the store. Well, turns out it was just a phase. The store bored him and being a typical boy, he really hated shopping ~ unless it was like a gaming store ~ but even then, he could look online at home and skip the actual store shopping. He had grown out of play dates and playgrounds. He hated roller skating and the likes. He always carried reading material and getting his nose out of a book was near impossible.
Sure, we could intrigue him out to things he was interested in like one year for his birthday we spent the day going to the parks that had the big cats (The Big Cat Rescue & Busch Gardens)but that would be cost prohibitive to do often. My spouse took him to see the Space Shuttle launch close up a few times, but even things like this didn't happen often enough to make it a weekly adventure.
The good news is age does in fact change this. When my son turned 13, he began to take an interest in people again. Now at age 14, he is actively involved in taken martial arts classes with adults and teens alike making many friends. Turns out that he really wasn't 'anti-social'. He was simply 'anti-interested'.
3) Arbitrary rules do not work. They never worked for my parents. They've never truly worked for anyone. Sure, you can make all sorts of miserable consequences but does it truly work? You might get compliance but you won't get growth.
Teaching the 'why' behind the reason makes more sense to me. My son knows that if he stays up late on a day he needs to be up early the following day, he will be too tired and grumpy. If he goes to bed too early in the evening, he is going to wake up extra early the next day, etc, etc.... I once had some lady give me crap that if I didn't force my child to sleep 8pm to 7am the next day, he would never be able to function as an adult and I was doing a disservice to society as a whole. Considering all the crazy shifts I've had to work in my life, I can tell you that her concept is totally off! The whole world is not asleep between 8p and 7a. Nor should it be.
So as far as 'arbitrary rules' go, what has worked better for us, is talking about the cause and effect of choices and learning to make wise choices. Yes, kids as young as eight can handle these sorts of discussions.
Well that's my $.25 for what it's worth.
May your New Year be blessed with laughter and joy!