Google likes fresh content, so do your readers. So why duplicate.
Duplication could be for some genuine reasons such as:
1. Replication to split traffic between two sites
2. Replication to monetize on traffic from different geographical locations
3. Distribution of content on multiple sites for a varied target audience or markets
4. Viral marketing or allowing republishing for a linkback
5. Distribution for multiple sites with different domain names – .com, .net, .org, .info, etc
6. Just for the sake of sharing data with partners, friends and family
In such a case, the best thing to do would be to format the text differently, instead of simply cutting and pasting the same on multiple sites. Use Similar Page Checker for tips to make your content unique. Google penalizes for substantially duplicate content which means you can have similar content, but try to avoid mirroring. To check if other sites have the same content as yours, use a popular internet tool called Copyscape.
If your content is duplicated on another site, the search engine filter would only display one copy of that content. Your site or page won’t be banned or penalized for minor similarities. But, substantial duplication could affect your Page Rank adversely or the site could altogether disappear from the Search Engine Results Pages (SERPs).
Too many articles published on a website in a very short span of time might appear to be fishy. If you ever publish sponsored posts, make sure you edit them, no matter what, in order to ensure that you do not have the same content floating on multiple sites. Ignorance may not mean bliss always!