I'm not a fan of noindexing pages as a way to control what ranks. The idea of noindexing a home page seems totally at odds with the way a user or a search engine needs to interact with a site on the web.
The immediately obvious problem with noindexing any upper level page that ranks, let alone a home page, is that... unless you have two pages ranking... you may end up with no pages ranking at all.
Beyond that... and this is speculation... possible distortion in traffic patterns could negatively affect pages lower in a site's nav hierarchy. It certainly would mess up "branding" and linking patterns.