Not having been devoted to SEO for some time I just did a search:

https://support.google.com/webmasters/answer/66359?hl=en
https://moz.com/learn/seo/duplicate-content
Duplicate content is a huge topic in the search engine optimization (SEO) space; heck, we even have a category devoted to the topic. But should we worry about it? Google's head of search spam, Matt Cutts, said he wouldn't stress about it — that is, unless it is spammy duplicate content.

SO, hear is my question:

Can Duplicate content hurt the target site in 2015?

There is a firm building sites for folks and sending traffic to my merchant.
LOTS OF SITES

Should I worry?
The Merchant site RANKS without tricks.

I think it is still a very big deal and should be avoided.

I'd agree, Google are probably quite aggressive about filtering out duplicate information as it has the potential to ruin a SERP.

Excerpt about shingling http://nlp.stanford.edu/IR-book/html/htmledition/near-duplicates-and-shingling-1.html

QuoteOne aspect we have ignored in the discussion of index size in Section 19.5 is duplication: the Web contains multiple copies of the same content. By some estimates, as many as 40% of the pages on the Web are duplicates of other pages. Many of these are legitimate copies; for instance, certain information repositories are mirrored simply to provide redundancy and access reliability. Search engines try to avoid indexing multiple copies of the same content, to keep down storage and processing overheads.

I've seen multiple sites tank (and I mean REALLY  tank) on panda updates thanks to duplicate  / canonical  issues.  Definitely a bit deal.

http://firstusahosting.com/

These guy are building sites and submitting to SAS

TOOK THEM ALL OUT

I'm thinking that they may be charging  MFs to build these sites

Anyway F em

Interesting... http://www.slideshare.net/jonathanearnshaw/is-your-content-working-better-for-someone-else

I have a couple of cases where we've taken content from another source (with permission), republished with small additions (say +15% word count roughly), and without any intention to do so, have ended up outranking the original.


if ($domain_status > $foo){
$link_value = $link_value ^ $bar;
}


The reason for my question was:

These MFs http://firstusahosting.com/

Have submitted 12 sites under 12 different names all the same content Promoting my merchant.
They have even placed their © 2015 Powered by First USA Business Development on these sites.

I'm thinking that they may be charging individuals to develop these sites.

I don't want my merchants rankings to be hurt my these "doorway" sites