Sheduling + forkbomb

Isn't it strange, that a simple fork-bomb, like a command to sh:
f(){ f|f& }; f
can get machine down. I've tried several times this thing, changing ulimit. (I've set a limit to user processes - 1000 ). The kernel didn't want to reply even on Alt+SysRq+H. Only Alt+SysRq+B could help. Of course, Ctrl+Alt+Del couldn't help because init couldn't spawn processes to procees reboot scripts.

My kernel is 2.4.18

Best regards.