This is a simple little plugin that adds a question designed to stop bots from registering accounts ( Such as 'What is three plus three?' ). The question and two acceptable answers (such as '6' and 'six') can be changed via a dashboard settings panel.
This has only been tested using basic registration, but should work with invitations as well.
Since this adds new views for the registration screens, I do not believe it will be compatible with other plugins that do the same (FirstLastNames)... Although it would be fairly trivial to combine the two.
Thanks to peregrine for his tutorial and jspautsch for the FirstLastNames plugin/discussion that answered most of my questions on writing this plugin.