It's a shame there are so many legal costs and constraints to applying for patents; we badly need a patent equivalent to copyleft.

We do. It's called the GPLv3.

Have there ever been any court cases where patents have been invalidated or upheld based on any flavor of existing copyleft licenses? And is there any way to apply GPL to the kind of broad concepts which are successfully patented ("One Click Purchase", as opposed to "OnceClickFramework::BuyNowFunction")?