Delurking to comment. I apparently was a biter as a toddler. While I don't know the litany of things that my mother tried to get me to stop, I do know that the only thing that worked was when she bit me back.

I'm guessing that, especially for young toddlers, they just don't understand that biting hurts the other person. It feels good to them (esp. since a common way to deal with teething is to give the kid something to gnaw on), so they don't necessarily make the connection. If overacting your pain as a bitee doesn't work, maybe a nip given to your little ankle biter might. Not because it's a punishment, but because it helps them understand that biting hurts!

Once, though, they're past the age where they comprehend that idea, other disciplinary methods should be brought to bear. (Not even going into the spanking debate; just an observation why biting a biter might be an effective way to stop their behavior, and why it's not tantamount to child abuse.)