[quote name='Wolfpup']I *think* that won't be an issue, as it's tied to your console, not the hard drive.
I'm still pretty sure this "gameshare" stuff is illegal though...[/QUOTE]
Sigh, i can't believe some people are still tied up with that crap ("game sharing" is illegal). Why can't people just enjoy the feature as a privilege? If you buy a game from PSN and if you have more than one PS3 (i have two and soon will get another slim for the basement), does it make any sense to buy the same game twice or three times? No! Granted that on CAG, we don't share the game as Sony's initial intention. However, in a nutshell, it's just another web of gamers sharing similar interests (instead of spreading the games among their own PS3s, they just spread the games across the PS3 community).
There are pros and cons to the PS3 account design, but one of the best thing about it is that, once you setup your account on a friend's PS3, you can earn trophies and stats from playing games on his/her PS3 without bring your PS3 to his/her house (vice versa). In the Xbox world, you have bring your hdd to do that (it's not a terrible thing, but i prefer not have to bring anything). There's nothing wrong with login as guest or even your friend's account, but we all know that as an avid gamer, you want your own space, your own saves, your own scores, your own achievements/trophies. This is another reason why game sharing is cool and Sony is not stupid, that's why there's a max of five sharing accounts.
As to backing up the PS3's hdd, i don't recommend a full backup just for the sake of backing up data (i.e. you're not upgrading the hdd). You just need to backup the saves (unfortunately not all saves can be backed up though). The PSN games themselves can be always re-downloaded. This should save you a lot of time when backing up game data (not the game themselves). Of course, if your PS3 has other stuff like pictures, musics and personal videos, then it's a different story...
But if you do backup the entire thing, the backup doesn't take up any sharing slots, it has nothing to do with sharing at all. However, if you ever restore a backup, some of the accounts might need to be reactivated (under management, reactivate account). As i posted earlier (posts a while back when i upgraded to 500gb), some shared games don't work even the status says activated after restoring a backup. What you need to do is to deactivate the account and then reactivate it again (like a light switch). I have no problems with my shared games.