How does a 301 hinder crawling? :\
How can Webmasters proactively address duplicate content issues?
# Block appropriately: Rather than letting our algorithms determine the "best" version of a document, you may wish to help guide us to your preferred version. For instance, if you don't want us to index the printer versions of your site's articles, disallow those directories or make use of regular expressions in your robots.txt file.
# Use 301s: If you have restructured your site, use 301 redirects ("RedirectPermanent") in your .htaccess file to smartly redirect users, the Googlebot, and other spiders.