Aye, I remember the 'Bite' option, and although it was before I ever spent much time on the forum, I still was kinda afraid of it. xD
I personally believe that having a positive-only Floof-O-Meter is best, though. This way you won't have people randomly launching bite-attacks on other users, and as Fantasyna said, you don't have to sit there worrying about something you might've done wrong, when really there was just some guy trolling.
It creates a more positive atmosphere, since people who don't say the nicest things simply don't get floofs. And conversely, as it's always been, people who say/do nice things get rewarded with floofs from the community.
Plus, I think it's a little ridiculous to still see some kids running around with -20 floofs leftover from the 'Bite' era. It happens, and it's a little sad. I'd rather see someone walking around in a neutral state on their Floof-O-Meter, rather than having them pre-judged in a negative way by everyone they meet, just because of their karma level.