The argument is slightly skewed because in the real world you mostly have “strong copyrights” and patents. So you can break an item apart, but you can’t create your own, using the same bits, and sell it as your own, at least in theory.
But LL wants to implement this “breaking apart” idea. You should read Cory’s blog for more input, but, very briefly, in the summer of 2005 or so, objects will have a “wrapper” or a “seal”. If you break that seal, you can see the contents, but you won’t be able to transfer the object to someone else – thus enabling you to understand how it works, but not to resell it “as your own”. LL thinks that people will be able to acquire more knowledge faster, and improve on existing designs, thus creating better and better content.
“Weak copyrights” are in place when you allow people to use your work by forfeiting several of your “rights”. To get a much more complete view on this fascinating subject, take a look at Creative Commons. According to what I’ve read, there have been many talks between LL and Creative Commons, a non-profit organization which is trying to bring new licensing models to the authoring world. You can see them as the Free Software Foundation for non-software authored content – music, images, video, text/hypertext. So things like the GPL or BSD licensing (which are widespread among the software community) are “converted” with appropriate legal wording to other “copyrighted” material.
LL seems to really believe that this is “the way to go” and is starting to pave the road for it to become a reality inside Second Life®.