The gentleman in this video, Dr. David Weinberger, thinks it’s a pretty terrible idea to try to categorise ideas in the same way we categorise physical things in the physical world.
Many people who deal with information on a regular basis tend to think that since you can only stack a chair in a single location, the virtual representation of that chair should be categorised in one place as well. It’s hard to explain why that’s a silly idea (and why it’s done often), but he does a very good job of doing just that.
He draws from a really neat reference: The Library of Babel by Jorge Luis Borges, and compares Wikipedia to Borges’ theoretical, infinite library (that, naturally, drives its librarian mad). That bit is in the Q&A period at the very end.
Thanks to Gil P. for this one.