We just had one of those "times" in our house, that I think that my boys won't ever forget. They'll recall it when they're older - the oldest one will remind the youngest one again and again and again.
Since mid-February, the oldest one has been working on Star Wars Lego for the Wii. There are 160 things that you need to get - minikits, power bricks, golden bricks, whatever. Each one unlocks some cool little trick or thing that makes the story/game more complex and fun. Each time you achieve one, you save the game. He plays that saved game nearly every day.
When he went to school on Tuesday morning, he has 130-something of these 160. When he came home, there were only 8. Eight.
Little brother had his turn and somehow reset the WHOLE thing. And didn't tell me. Until chaos reigned when it was time to play for a few minutes after homework. There was freaking out and panicking, then blaming of the faulty nunchuck by the child who can't read. It was kind of a disaster all around.
We've achieved some kind of peace - for one week, the older child has usurped the younger child's time allotment for the Wii - to help him build back his hard work and to punish the younger one. On the plus side, the middle one is happy, because she has her playmate back for a week.
But over dinner when they're adults, they'll tell their children about the time that the little one deleted the older one's game. Hopefully the bitterness will have dissapated by then