There are many opinions about what duplicate content is and when that can attract a penalty. Here is a different opinion then what you read:
http://searchengineland.com/070315-100022.php. If you will read comments though, some will agree, some will not.. some are much too obsessed with percentages and numbers... truth is nobody knows what google consider duplicate, and what is the "bad duplicate", otherwise we all could avoid it. If 8 consecutive words would been a trigger, then we could just take any text and change every 6th or 7th word to something else and avoid filters.
I think the most legit opinion should be google's itself:
http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=66359As you can see that say "Duplicate content generally refers to substantive blocks of content within or across domains that either completely match other content or are appreciably similar. Mostly, this is not deceptive in origin. [...] Duplicate content on a site is not grounds for action on that site unless it appears that the intent of the duplicate content is to be deceptive and manipulate search engine results". In my opinion 8 words is not a substantive block of content, not to speak about deceptive intentions. When one intention is, for example, to give some articles to read to his/her users, having some free articles in a site is not deceptive at all, even if those articles are existing in exactly same form on other sites.
