When the startup lawyer says that the protections for parties in startups from defection and unfair competition are derived from IP laws, I tend to believe him. You seem to retort, "but that's contract law!". But those are contracts protecting intellectual property.

Postgres, sqlite, BSD, and clang are BSD-licensed open source. But many more projects are GPL-licensed, and thus depend entirely on IP law, than those that aren't. Without IP law protections, those GPL projects compete on an unlevel playing field with companies that would otherwise be free to capitalize on all their work without contributing anything back.

Finally, of the list of YC companies here: http://yclist.com/, how many take no advantage of IP laws? How many are entirely BSD-licensed open source? How many have no trade secrets?