Robin Good: Here's a great visualization of how different can be the traits of content re-use. In the left column you can see what would appear to be the ideal traits of a professional curator, while on the right you can immediately recognize the ones of scrapers, republishers, cheap aggregators and other "thin" publishers as Google would call them.
I think it can serve as an excellent reference, when in doubt about whether you are still doing the right thing or not, when it comes to re-using and republishing other people content.
The table is part of an excellent presentation entitled "Link Building by Imitation" and authored by link building expert Ross Hudgens.
Via Robin Good