Just my opinion...
If I find something interesting and useful, relative to a blog I maintain, it's helpful to
- the original source,
- to my blog,
- and to my readers,
if I properly "curate" it.
By "Curate" I mean (loosely) an introduction, the copied excerpts, and the attribution.
My readers get the benefit of the information, the originator gets a link to his article, and I will hopefully gain viewers.
DrudgeReport.com, Google news, and HuffingtonPost.com get their content via Curation- at least my definition of Curation. They would dry up if they couldn't copy excerpts and make appropriate links.
IMHO, if you copy an entire article (so the reader doesn't have to link to the original) then you are probably guilty of copyright infringement. But an excerpt, or opening paragraph, with links and attribution.... I don't see who is being harmed.
Copying the article, mashing it through a rewriter, and sprinkling in some Content Injection may help get clicks, but the result is usually less useful (and a bit less honorable) than just plain Content Curation.