TheOptimizationIdiot - 7:49 am on Mar 18, 2013 (gmt 0)
Exactly why I usually "totally cover the bases", which means: Set WMT to disregard, canonicalize anything sorted or duplicated, and also noindex anything sorted or duplicated.
there's no "penalty" for duplicating content. You're just serving unnecessary content to Google that leaves it to sort through and make decisions - essentially, handing over control of how your site is crawled and indexed for a third party to decide, based on their particular criteria of the time. Fixing such problems has nothing to do with penalties, and everything to do with controlling your site's destiny. It's old school tech SEO.
Absolutely. They "group" or "cluster" duplicate URLs together and then try to figure out which one to "give the weight to and show", so you're not really ever penalized, but letting them figure it out on their own can have unexpected results.
Duplication can also "stall out" crawling due to multiple URLs with the same content being crawled and taking cycles away from different URLs, but as far as onsite duplicate content goes there is no penalty.