Plagiarism is defined as:
the act of using another person's words or ideas without giving credit to that person (Merriam-Webster Dictionary)
Is plagiarism checking necessary?
The Internet, although being extensively beneficial suffers from a major drawback, which is, enabling almost effortless plagiarism. Rising concerns over, “intellectual property theft” due to cyber-plagiarism, specifically from students, and content writers (bloggers, writers, and other professionals), has attracted a high degree of interest from educational and professional institutes, the world over, to design effective and innovative techniques to check for plagiarism all submitted work. Universities, colleges, schools and professional concerns are not interested in excuses anymore and penalize offenders using the strictest measures. These can result in individuals or institutions getting fined (up to US$ 500,000), prosecuted, failing or even getting fired from the concerned institute.
With the government regulation on SOPA and PIPA it has become ever more important for professionals and institutions (not just students) to check for plagiarism before publishing.