Why does blatant and obvious abuse continue in Yahoo Answers?

I think there's several reasons. One is that people can have some level of remaining anomymous, and behind the computer screen it feels like they can safely say what they please. Another reason is that Y!A does damage control with the deletion of many questions and answers, and it makes some people feel as if that's a clean slate for them to do it again. And if someone's account is suspended, they can just come back with a new one and start over.