is turning off the ps3 while playing a game bad?

I've done that and haven't had a problem

I wouldn't do it on a regular basis but it shouldn't hurt anything if you do it occasionally.

Yes in my opinion because it's killed three of my PS3s. It's even worse when it's frozen because either way it messes up the disc tray unless you have the most recent model of the PS3 with a open disc tray. Just press the PS button and "Quit Game" before you turn the system off. And especially in the older versions, take the disc out, don't leave it in the system for a extended period of time because that'll mess up the disc tray too, trust me, I use to do that too even when I would just play Battlefield 3 over and over and over rather then taking the disc out and inserting it back in everytime.

No it isnt but you will lose all of your unsaved data from GTA IV.

how else are ya gonna turn off the ps3? remove the disc first? of course its ok.

no, but why do that?