A very common form of plagiarism on the Internet is people copying transcriptions of public-domain works without mentioning where they copied them from. You kno

A very common form of plagiarism on the Internet is people copying transcriptions of public-domain works without mentioning where they copied them from. You know it's happening because you see the same transcription errors repeated on dozens of web sites. (Of course there is no copyright violation here.) A very common case of copying without attribution is in contracts and policies, which are nearly always adapted from existing documents. Probably this doesn't count as plagiarism because nobody expects these things to be original, authors are not named, and there is no tradition of citing sources. (However, in many cases it probably is copyright violation, even if nobody cares to complain about it.)