In high school(4 years ago) I was required by some teachers to have only a certain number of citations from a number of given source type(encyclopedia entries, magazine/newspaper articles, internet sites, or books).
To get around that stipulation I would at times take an article from one format and shift it to the other. This occured most frequently with internet sources. Since the internet wasn't different from how it is today, teachers would put a strict upper limit on the number of internet sources I could have in a given paper. I would take magazine articles or newspaper pieces and make my citation look as though I had gotten the article from its equivalent hard copy source. Of course this wasn't true just because our small school library didn't have the amount of media that would have required. I never got any comments on it however. So obviously the teacher just took the citation at face value.
The only time that could cause issues is if one would have to cite the page number of an article. If I couldn't look at the "original" form of the article I would have to change how I cited it. Even that is silly though because if one prints out an article by hand according to the MLA citation style one cites the page number based on that given printout. That loses any meaning if the paper remains in a electronic format since the position in a printout of a given section of text can change based on a number of factors the simplest being font type and size.
Fred Wilson points out that his daughter recently ran into this stipulation in a paper she was working on. He mentions that it is to prevent "instant gratification" and "cut and paste" paper writing.
I don't know how much such a policy really matters in the long run. While in college many students will write a paper a short time before the due date. At this point in time only internet resources are available for easy access. I have turned in many papers in my college career that have been cited by internet resources only. College professors have accepted the fact of simple internet research methods and don't make the kind of requirements that I ran into back in high school.
With the movement of resources from paper into a digital media in a short time students best resources will be available online. These sources are more relevant and most likely more current. I assume over time those stipulations wil morph or disappear entirely.
Fred makes the interesting point of possibily using internet technologies to create a fluid research paper environment. It would be interesting to figure out what kind of shape such a technology could take. I can vaguely see how wiki's or blogs could be used to make such an environment. Students would post rough drafts of papers and allow for comments on the papers. Maybe not allowing removal of content but just suggestions of what could be improved. This would allow the words to be the students and with a history of the paper the teacher could easily see how the student incorporated the ideas of others.