I agree with one of the previous posts, the witness protection part was just a witty name that somebody at SOE came up with for the item combo pack. As far as being able to be tracked by a number, I don't think players should be able to track eachother that way, they shouldnt have access to that type of info. On the other hand the GMs at least should definitly have some concrete way that only they can access, so that they can tell if a problem player (and i'm not insinuating you are one but for the sake of argument say that someone is) is the same person with a different name.
Just like witness protection in RL... Someone tries to murder you, they put you in the program, whosever coming after you doesn't know who you are or where to find you anymore, but its documented and the authorities will always know who you really are and will know something is up if a 2nd person tries to murder you, then theyd figure you're doing something to instigate the behavior in others.
So I guess to sum things up, imho should players be able to track you? No. Should GMs be able to track you regardless of a name/sex/race change? Absolutely. In my head if the first player is the problem, and wants to start fresh fine, but he'll prolly end up back where he started, and the GMs will know who it is. If the first player really wasn't the problem and wants to start fresh, then he should be able to and there shouldn't be anymore problems, but even if there were, the GMs would have the info on hand to know who is doing what and if it's happened before.