We bought a very expensive bike for ds2 last year, well about 14 months ago to be exact.
He hasn't used it that much but we took it out at the weekend for a family ride. It has some quite good stabilisers that attach with a hand-grip bolt, which simply unscrews when you want to stash them and have a proper go without.
We got about a mile up the hill and one of them fell off - I found the remains of the threading from the frame around the threads of the bolt.
The threads have sheared off after maybe a total of an hour and a half's riding on it if that.
I contacted Specialized who said go through the shop but they would replace the frame as it has a lifetime warranty (I should think so at that price - we got it as an investment for ds2 and ds3 as well when he is big enough)
The shop have contacted them and said this is a known issue apparently, and the guy at Specialized had to replace his child's with a normal bolt and nut and said it was 'much better' 
I have said no, this isn't acceptable - I need to be able to take them on and off easily and quickly and so does my son when he is out on his own.
I wondered if anyone else had had problems - I'm still waiting to hear from them about replacing the frame.
Its a lovely bike apart from that but I am cross that it is sold with all these little touches that make you think, yes that's worth it, and then a sodding wheel falls off. Apart from anything else he could have been hurt.