Wow, there's been a lot of activity in this thread. Please forgive me for not reading it all, but IP is something I've thought about for a significant amount of time and have even written about.
I'm not convinced that there can be no ownership of ideas, but I also think, like Jefferson, how when one idea lights the candle of another's imagination, how can it be put out? ...Which is my way of saying, (less eloquently than Jefferson of course) that once an idea is out there it's out there, and there's no way to put it back in. It's pointless and counter-productive to try.
That's why I advocate something called "compulsory licensing." It basically means that all ideas are up for grabs (and sale), but the original creator still retains some ownership in them, but not the ability to prevent others from using them.
For instance, under compulsory licensing someone could theoretically rewrite
Harry Potter as
Larry Potter and in my view they have contributed something new to it. Perhaps that change represents .00001% of a modification from the original. That amount can be decided upon by the two parties, or if they can't agree, by a court.
The second user then has the ability to vary the price, up or down, by the same amount that they contributed to the new product. So, if the original price was $15, the second user would have the ability to sell their reworking of it from anywhere between $14.999999 to $15.0000001. You get the idea. This is obviously an absurd example, but the principle applies to everything.
This is the only idea that prohibits both a monopoly of ideas, and not rewarding intellectual creation, which despite what some people at Mises tell you (an org. that I love and have written for by the way) having no property rights in ideas does discourage creation. People have committed suicide over it, people have been driven into poverty because they did not receive compensation for their ideas and the hard work that went into developing them. Just take a brief look at
Piracy by Adrian Johns and you will see evidence of it, yet this evidence is never, that I know of, mentioned by the no-IP crowd.
For an essay I wrote on the history of IP and the possible solution of compulsory licensing (I know libertarians hate the word "compulsory," but someone else came up with it, not me), see here:
http://www.globalresearch.ca/index.php?context=va&aid=19959