Can you imagine the number of "if you kill cheese weapon you can revive Cid" type rumors that'd come into play?
I'd have to disagree, I'm afraid. Killing off one character is okay in my book, it just adds that little something. It can't really be overused either, because you don't really know who will die until it happens. But when you go overboard things can become alittle depressing. Consider FFIV - FFIV SpoilersOne of the worst parts of the game, in my opinion, is when about four of the main characters die just to free up space in your character slots. I realise only one character actually died, but I didn't know that at the time, so I got really depressed that so many people died. Also I know I'm not the only one who got annoyed by it.

Plus Aeris' death was nice and memorable. If Cid had died then she'd be just part of the crowd of those who died, rather than the one who dies.
If Cait Sith had died the game would be much better though. ^_^