How do I expect that? I don't. No one would, or could, reasonably expect that in this game. I promise you, and I don't make promises lightly, that I'm not a werewolf, vampire or what-have you, now. I may be in the future, sure, I can't control that, but I guarantee you that now I am a Seer, and only a Seer.
To be honest with you, I wouldn't tell you or the village if I was infected, just because that would be extremely unfair to the werewolves. Unethical in my opinion. If you are infected, fine, you are now on the Werewolves side, not the villagers and have no responsibility to tell them that you are. It's not a matter of being good or bad: it's just the side you are on.
That said, I wouldn't lie about who I was. Period. And I respect chrmjenkins for not lying, in my opinion makes the game much more interesting. Even if it was for the betterment of my side, I wouldn't lie about it, and regardless of how everyone else feels about that (if you would like to lie and be dishonest in the game, that's your choice, and I respect that and how you play the game) that's how I play.
Now, I don't ask you to believe me, because I wouldn't. Just remember, you've only got one Seer, otherwise you will be lynching, essentially (let's be honest about this), blind. Lynch me as you like, but you will be getting rid of the only real way to tell if one person or another is a villager, werewolf, vampire or anything.
That's my position on the matter, and you may detest it, disagree with it, or vilify it and that's your prerogative, but that's what I'm doing in this game (and the ones before). I don't ask you to believe me, I wouldn't, just believe in me, and believe that I'm not lying to you.