There are a lot of variables in your question.
There are different sorts of duplicate content, for example the same product may appear in different pages on the website that is ok. However, if you are talking about long form content such as a blog copying and pasting this will definitely get you in trouble sooner or later.
Aside from Google at very least you will have a copyright issue, the original creator of that content owns it where ever it is published and it is a breach of copyright to reuse or publish without their permission.
The reason they haven't been penalized could well be Google hasn't found it yet or it could be they were the original creator. Google is very clever working out duplicate content the most likely thing you will notice is the page simply will not rank in Google.
If you repeatedly, copy content Google will eventually see your site as 'no value' and you could encounter a penalty or at very least a downgrading in ranks across all pages.
