Plagiarism vs. Copyright Violation - compare and contrast.
For copyright violation to occur - ownership matters, e.g. public domain; wording matters.

Most or all Federal Government documents are in the "public domain".

What is this? How does it affect copying from them? When does this matter?
Are there academic rules/regulations?
NC State University Code of Student Conduct (higher ed institutions generally have similar codes)
8.4 "... Plagiarism includes, but is not limited, to the following actions:
(a) Representing the work of others as his or her own; or
(b) Submitting written materials without proper attribution or acknowledgment of the source.

Does it happen?   On-line Paper Mills ~     YES!!!! How about in the writing of professionals?

Title: Past imperfect : facts, fictions, fraud-- American history from Bancroft and Parkman to Ambrose, Bellesiles, Ellis, and Goodwin
Author: Hoffer, Peter Charles
PublicAffairs, c2004   DH Hill Call Number: E175 .H54 2004

Introduction : two-faced history
Ch. 1. The rise of consensus history
Ch. 2. Professions of history
Ch. 3. The new history and its promoters
Ch. 4. In the eye of the storm
Ch. 5. Falsification : the case of Michael Bellesiles
Ch. 6. Plagiarism : the cases of Stephen Ambrose and Doris Kearns Goodwin
Ch. 7. Fabrication : the case of Joseph Ellis
Conclusion : the future of the past.

But in academic studies - lack of learning matters rather than theft

• shortchanges the student
• devalues the course credit & degree

Should chance of detection be a consideration?

Ethically, no - practically, yes ~ What do you think?

How is it detected: above by authors noticing own work, or readers noticing

Also when specifically looking for it: Using Technology

• A free challenge method
  Theory and discussion

• Turnitin.com a commercial service for higher ed (there are others - see Resource Pages)
  The Similarity Report
  Plagiarism.org an educational resource developed by Turnitin.com, which has resources for preventing plagiarism. iThenticate the commercial (non-edu) version of turnitin

• "A Web-Enabled Plagiarism Detection Tool" by Colin J. Neill and Ganesh Shanmuganthan in the Sept-Oct 2004 issue of IT Professional pp 19-23.

• SafeAssign"SafeAssign compares submitted assignments against a set of academic papers to identify areas of overlap between the submitted assignment and existing works."
• Copyfind/WCopyfind software for detecting plagiarism and other Plagiarism Resources
• SPlat the Self-Plagiarism Tool
• The Ethics of Self-Plagiarism A good description of what this is and associated problems
• Plagiarism Checker "a free online plagiarism detector tool"

• Do your own search - put quotes in a search engine
  e.g., many facets to understanding plagiarism "

  The Low-Down on Escaping Detection: whether High-Tech, Low-Tech or No-Tech

• Copy whatever you want (from the "original" work(s))
• Change the ideas so they don't resemble the original
• Reword so no more than two significant words in a row are the same as in the original
• Reword so that the vocabulary used is not the same as the original
• Read it over multiple times and work with it so that you develop extensive familiarity, and (preferably) it is in your own personal writing style

Or, as my mother said, "Crime does not pay well."