These are big issues in library studies, too, by the way. If a library owns a book, it has the responsibility to keep that book from being copied in a way that violates copyright, AND it has the responsibility to preserve it so that the information will be accessible in the future. If the library only owns a share of a resource for a specified time period, then who is going to preserve it? The ground is shifting.

But I’m afraid Daniel’s position in this case is very weak, even if he is correct. The problem with “crowd-sourced” sites like Wikipedia is that attribution is difficult, if not impossible to prove. Daniel can go back an demonstrate that a specific user posted specific text/changes at a specific time. But how does he prove that he is that user? As a student, the onus is on Daniel to prove that he did in fact originate the text over which he claims authorship. The teacher is right to be skeptical, otherwise every student that comes down the pike is going to plagiarize off the Web and claim original authorship.

Daniel may be able to prove his point. If so, he should have armed himself with that evidence beforehand. The teacher is under no obligation to accept his word. Far from it, in fact! The responsibility lies with Daniel to prove his claim, and he should marshal that evidence BEFORE handing in the assignment, not cobble it together after the teacher finds the matching text.