Yeah, it's a pretty amusing site. I remember playing around with it and making it guess various semi-obscure Discworld characters. That damn thing got pretty much all of 'em.
From what I understand, it records all the right questions/answers under whatever character you were making it guess... So the more people do it, the better it becomes at finding the right character because there's a growing database of facts about them. So that's why it asks you to type in the character if it doesn't guess it...
So, by that logic, if everyone started giving false descriptions to some characters, and by everyone I mean literally tens of thousands of people, you might be able to completely fuck it up. Make Gandalf a sparkling teenage vampire who turns into a wolf =p
But then again I guess that all of the better known characters already have too much of a database behind them to test this theory.