Say we have a domain, example.com, and I just want the site to be viewed under www.example.com.I know that the best practice would be to redirect example.com to www.example.com.  However, if this isn't an option and the naked domain is left un-configured, will this harm my PageRank?
Will a naked domain that isn't setup hurt PageRank?
seo;pagerank
This will not make a significant difference as long as the domain remains unconfigured and doesn't show any duplicate content - for example a copy of the main website as that would be considered a bad practice. 