Well, to add my fuel to the fire ...
DP and I sent our 18mo DS to stay with his grandparents for a weekend. They live about an hour and a half away, but neither DP nor I can drive, so it was my PIL picking him up and dropping him off. Sure, I cried when he went, but he had a good time, and it meant that DP and I got a break - we didn't have anyone who could simply pop over and babysit of an evening at the time. I used to stay at my grandparents all the time as a small child, as did my sister, and, now okay, it was much closer than the four hours mentioned here, but I guess I don't see that much issue in distance. For me at least, once you get to the point where it's a car journey it's a car journey further than I can go.
Of course, the reason he stayed there was that it was the only way for him to get some quality time with his grandparents without us around, as they're too far away to take him for an afternoon or a day. And we had often stayed at their house so it was familiar. I wouldn't do it with anyone else.
I'm in agreement with the people who say that being overprotective just sets children up for a stressful childhood. Okay, so it's not staying away, but I was sixteen before I knew how to catch a bus, because my mum didn't think it was safefor me to get one home from school. I can clearly remember being terrified the first time I was on one alone, because it was an unknown to me. And that's a bus. I can only imagine how scary it would be to get older and never have slept away from your parents.
Frankly, if I'm worried or a bit tearful at the thought of my DS going away, that's my business, and not his. His business is to have fun and grow up as a confident young man, which he won't do if he's weighed down by my neuroses. I used to not tell my mum about sleepovers or just visiting friends for tea because I picked up on the fact that it was "inconvenient" for her to have to drive me there or back. I missed out on a lot of life because I wanted to be a good daughter, and in the end it did me no good at all. It's not a pattern I want to repeat.