When should you use the google reinclusion request? When your site totally disappears from Google? When your whole site, but three pages was wiped from the google index and the remainder are showing supplemental and getting no traffic from Google? What if you believe there was nothing done wrong according to webmaster guidelines? What if that site has major authority links to your site? When should you actually file for a google reinclusion request?? BTW...WTH Google??
I would file one for any of the above. Make doubly sure you haven't bought loads of links and that your site doesn't sell links or link to any dodgy sites first. Also make sure the content is first class.