The Mollom Ruby SDK by Joren De Groof allows to evaluate quality content via API. Usage demonstrates how captcha can determine if a user is spam. Additional code could remove the spammer if content is unsure.
Your phone may soon be all you will ever need to carry around. Up until now, your online identity and the real world hasn't mixed. We have ways of authenticating offline and different methods online. Enole is trying to fix that, with an uncomplicated RESTful web service that enables developers to store user details alongside a mobile device ID.