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.
A few months after Facebook announced a new app review process in the wake of numerous Facebook app-related scandals, Facebook is about to make the process automatically enforced. To date, developers have had the option to enroll for review, or avoid the process. That is changing soon.
If you run a website, like many of our readers, and you have an account system, you probably have problems with spam. One of the main sources of spam is users who register using disposable e-mail addresses. These can be generated by spammers programatically, using services like the Guerilla Mail API I covered previously, and used to make tons of accounts to try to get blog spam through. If this is a problem for you, the DEA Filter API can help.