I'd get mad if someone deleted a save for a game that i was currently playing or recently played. I wouldn't be mad if a really old save fiel was deleted, i'm using it anymore right?
i actually delete my old saves and give the free space to my bro or sis. like in Zelda TP, only 3 slots, so i deleted my save and gave it to my bro, the other two were already taken by my other brothers (i have three brothers and a sister). i didn't mind cuz i had beaten the game long ago at the time. same thing usually with every game with limited saves.
the only exception was NSMBWii, everybody wanted to play at the same time lol, and each save file only had THREE slots... so i had to get another SD specially for a second save file and each time i wanted to play i'd put the first save on SD1, then copy mine from SD2