I do get a kick out the denial that duplicate pages get penalized. Tell that to anyone who does affiliate marketing using merchant data feeds.
Getting tagged for duplicate content is a random process. Sure, Google says it is not a penalty, but is really a filter. I can understand that. But if a duplicate content filter reduces the ability of a page to rank well, it sounds like a penalty to me.
If it walks like a duck, and quacks like a duck. . .
Beyond the risk of duplicate content issues, there is a much larger issue when you duplicate entire sites. That sets you up for a mirror site penalty. Over the years I have seen numerous situations where mirror sites have dropped out of the search engines. Sometimes the original site disappears when a pirate duplicates an entire site under a different domain. IMHO, the same site should never show up under multiple domains.
Just read the search engines' webmaster pages:
Webmaster Guidelines
Google: Don't create multiple pages, subdomains, or domains with substantially duplicate content.
Yahoo! Search Content Quality Guidelines. - Yahoo! Search Help
Pages Yahoo! Wants Included in its Index: Original and unique content of genuine value
What Yahoo! Considers Unwanted: Multiple sites or pages offering substantially the same content, Pages that rely heavily on content or links to content created for another web site, such as affiliate content