I think credit has a lot to do with it. Also, feeling like you "own" your idea is largely cultural. We live in society where just ideas alone are sellable (corporate world especially). We have been taught since college that you do not amount to anything without ideas even though your ideas are built upon ideas of others, we do not teach that kind of connectivity, we do not teach "collective knowledge." What we do teach is publishing a paper and copyrighting it. One of the most prominent questions I have from faculty I work with in regards to creating a public professional ePortfolio is "What if someone copies, steals my idea or paper?" and "How do I make it so that only particular people can see it?" I am sure stealing does happen because there is a lot of pressure in academia to "generate" ideas. And I am also thinking that publishing your copyrighted idea in a peer-reviewed or any other academic publishing instance gives your work "validity." But if the mind set we build in our students is ownership-oriented how can we expect anything else?