Creative Commons gives people the opportunity to share and borrow information. Should creators feel compelled to share their work in order to make this free culture work? Are there any instances where a piece of work should not be shared?
I don't think there is a general obligation of all creators to share. I do believe there's an obligation of academics to share. Creators need the freedom to earn if they're to afford independence. Academics (at least some) are given that independence, through tenure and a salary. They serve the enlightenment; other creators serve whatever values they wish.