My own academic training (undergraduate and Master's, political science and business, respectively) was pretty strong on the ethics aspect. I know better than to copy sentences without attribution. Or to copy sentences with minor changes.
When it comes to plagiarizing yourself, I'm a little fuzzier on what's acceptable there. In the corporate world, government and even the business end of academia, memos and announcements go through multiple drafts. It's typically a little unclear about how gets credit for research not so much because a manager claims credit for research someone else did, but because any research is so often a collective product.
That's a wide generalization, and I know there are specialized rules for scientific research. And, in general, employee evaluation systems should give individuals proper credit for their contributions. But lifting a sentence from another memo on the same subject, especially on some more-or-less procedural matter, isn't considered anything unusual. In accounting, using the exact language of the official accounting standards or the company's accounting manual is often preferable to paraphrasing it, since precision matters.
It depends on the situation, of course. And if someone is selling text in some way as their individual product, that's another matter.
The blogging I do isn't exactly academic. And it's mostly not original journalistic reporting, either, though I have done some posts that I would argue qualify as journalistic. What I mostly do is opinion commentary, analysis and synthesis.
For instance, in a recent post on Todd Akin and the anti-abortion movement, I brought together material from three different articles: a current news report, a current blog post, and an analytic piece from 2011, and related them all to the long-term radicalization of the anti-abortion movement and what I see as the inadequacy of the response by the Democratic Party.
That post did present a question that sometimes occurs about attribution; the Mother Jones article I cited was linked in The Nation article I also cited. Should I have mentioned that I found the one via a link in the other? In this case, I didn't, and I don't really think in general it's necessary. But sometimes I do. For instance, if I see a quote from Article 1 in Article 2 and use the same quote, I'll normally mention that I found Article 1 via Article 2. But I also make it a practice to go the original article, so I see the attribution to Article 2 as more of a courtesy than a necessity. On the other hand, if Article 1 was something really obscure or newsworthy, I would feel more strongly that I should cite the person who found it, or from whom I got it.
I make it a practice to cite the name and author of the articles I quote. There's nothing wrong with just linking to the article; that is valid as attribution in a blog post. I started doing the full citation early on in my blogging career, which began in 2003, because I got so frustrated at dead links. I found it was easier to locate an article I had previously cited where the old link was dead if I had the actual title of the article.
I'm also very mindful of the rules of Fair Use and the legal guidelines for blogging. The Electronic Frontier Foundation is a helpful resource there.
I've been thinking a little more lately about self-plagiarism. The first time I recall even hearing about this was in an article about historian Steven Ambrose in which he had taken some material from earlier works of his. My first reaction was, so what? (Ambrose was accused more seriously of plagiarizing other work, as Wendy Kaminer discussed in Heavy Lifting The American Prospect 01/31/2002.
But I know there is an issue if someone is paying you for original material or if you've committed explicitly to provide original material. As David Carr writes in Journalists Dancing on the Edge of Truth New York Times 08/19/2012, speaking of a self-plagiarist, "rerunning parts of his books and previous writings for different publications ... is an offense against his employers, not his readers."
Steven Brill in Stories I'd Like to See: Fareed Zakaria's 'mistake' Reuters 08/21/2012 takes issue with Carr's evaluation of the seriousness of Zakaria's plagiarism.
One of the bloggers I respect the most, Digby of Hullabaloo, generally designates material she takes from her own earlier posts as being such, and sets them off in her blog's style for quotations. If I'm referring to an earlier piece of my own, I'm more likely to link the earlier post and take a portion of it and use it nearly verbatim on the point I'm making. Since this is a non-commercial blog, I'm not ripping anyone off by using the same wording.
In any case, the same writer making the same point is likely to use very similar words. Blog posts aren't like a politician's stump speech that can be given over and over for a period of time with only minor variations. If every post were almost the same every day, that would be kind of pointless. I could save a lot of time by just linking to the first one.
Jonathan Bailey has a brief, accessible discussion of the relevant issues in Self-Plagiarism: Ethical Shortcut or Moral Scourge? Plagiarism Today 11/07/2011.
Michael Bartel in Cut, paste, plagiarize Salon 08/14/2012 suggests that part of Zakaria's problem is that he is not familiar enough with how Web research works:
The plagiarism charges revealed at the very least that he was a lazy writer, most likely reliant on an army of uncredited assistants to construct his columns and then insufficiently careful in processing their work. It revealed the supposedly superior practices of the mainstream media as not noticeably different from the messy, chaotic process of blogging. Both were acts of massive collaboration and repurposing carefully covered up so the seams didn't show. When Zakaria’s plagiarism was discovered, it was the rare moment when the Web's standards aligned with the mainstream media’s, and he was out.And he observes, "The way you demonstrate your trustworthiness to a major media company (credentials, qualifications, professionalism) is almost diametrically opposed to how you demonstrate credibility online (transparency, reputation, accessibility)."
Bartel goes farther than I would in suggesting that it's normal and generally okay to borrow stuff without attribution in "Web culture." That's not really conducive to transparency and reputation if you expect people to take what you say seriously and based on something other than what you would like to pretend to be right at any given moment. I know that works for FOX News and Rush Limbaugh. But if you want a good reputation in the reality-based community, it doesn't.
Andrew Burstein and Nancy Isenberg approach the issue by looking at the difference in approach between journalists and historians in America's worst historians Salon 08/19/2012. (Full disclosure! I got the Bartel article from a link in the Burstein/Isenberg one!) Their piece gives voice to the perennial gripe from professional historians about amateur ones and about "popular" history even when written by professional historians. This comment particularly grated on me, "Bear in mind that, as a matter of course, history majors are taught to visit the archive and focus on primary sources. Government majors are not."
Yeah, bite me.
Kevin Levin harshes on them in Andrew Burstein and Nancy Isenberg Know Who Owns History Civil War Memory 08/20/2012.
There's a blog on the University of Michigan website that deals with copyright issues, called Copyright Librarian. This post from 05/01/2012, Free and Legal Stuff You Can USE! by "nasims" is a useful collection of resource links.