I have actually a silly question, but where does your trophies being saved? Into your harddisk or to a Sony's server?

My brother-in-law did a format and lost his GTA IV trophies though.

Another question may arise, that how you can make a completely backup of your PS3 HD (I normally copy my save games to a USB stick for backup), including trophies possibly?
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I think the trophies are saved on a server, because the first thing the PS3 does when you add a new HDD, is synchronizing your trophies.
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I also think the same because when you go to look at your trophies the PS3 has to sync them before they are shown, and the same if you compared them with a friends trophies. Could be wrong though. It might save them to both the network and locally. It definitely has to save them to the network though, otherwise how would anyone else in your friends list be able to compare them when you are offline?
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If they're saved on your hard disk and then synced to the server, what's to stop you hacking the files for better results and then syncing it up to the server?
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There probably isn't if you knew how. No software will ever be 100% secure or fool proof and will always eventually be able to be hacked.
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There are trophy hacks existing, even PC applications to deal with them, never tried though, I don't see the point.
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