Yeah, but the API doesn't give you access to those users' gender (since Twitter doesn't ask/store that info), which means you have no way to tell the classifier "Here are 500 males' tweets, here are 500 females' tweets."

I suppose you could manually find males and females and train based on their body of works, but it won't be great; you'll likely run into a selection bias.

But if you seeded with that approach, and then used a SpamAssassin-style auto-learner...maybe you'd have a chance?

I suppose this is a case where you don't want "Perfect" to get in the way of "Good enough", especially since it will never be perfect...