this would only make sence if the exploding was st. programed in on purpose...
Well, I think it's more that when they realized that the number of character files was causing certain uni bugs, they "fixed" it by making the game able to handle more files before these problems occurred. There was some kind of reason they couldn't just remove whatever causes it, but they upped the limit with the uni patch and I assume they have continued to do so as they have released expansion packs that added character files. But you know how it goes when you assume things.
I believe it was just number of character files, which includes all dead sims and all sims in the family trees of maxis made sims. And I kinda assume pets are going to be included. I'm well under 1500 at the moment, so I won't worry yet.