Reverse SEO is a way of making sure you rank high in the long term. It is the complete opposite of regular SEO, which we know Google hates. Google is cracking down on SEOs as the recent Penguin update is evidence of. So reverse SEO is doing the things Google aren't expecting from SEOs = ranking win. Like putting up posters with your domain name written large on them all over town so that when Google streetview cars drive around they will OCR your poster and give you SEO juice for it.