Additionally, to own copyright, you would actually have to _create_ a product/movie/etc. How any patent holder can sue without actually creating or using their own patent is beyond me.
mluiten might be referring to the fact that copyright only applies to "original works of authorship fixed in a tangible medium of expression." (See http://www.copyright.gov/help/faq/faq-general.html)
That is, copyrights don't cover ideas, but creative works in some fixed form (e.g., a painting or a piece of software).
Say you've got a popular photo, you can transfer the litigious rights of it to a copyright troll and that troll will then sue everyone using it.
Kind of like what RIAA is doing.