people should have ownership over ideas
Any ideas that I have are, to a considerable (possibly entire) extent, inspired or formed by the ideas that I've been exposed to prior to coming up with "my own" ideas. Really, when you think about it, can any creator take 100% credit for whatever it is they produce? Take philosophy for example, when someone writes up a book with some new philosophical theory, it's guaranteed that the ideas of philosophers going back centuries contributed to the new work.
Maybe the best example is chord progressions and jazz music. A whole pile of great jazz tunes were based on the chord progressions of songs by old timers like Gershwin - jazz artists would take the exact same chords, write new melodies, and improvise great tunes out of them. Imagine though, if copyright law had included chord progressions - jazz music as an art form would likely not exist. And really, why shouldn't chord progressions be copyrighted too? After all, Gershwin came up with some great ones. But the loss to society and culture would have been severe (although nobody would have noticed at the time). And at the same time, Gershwin when he wrote those chords would have been inspired by the musicians of his time that he listened to. So jazz musicians ripped off Gershwin (and other tin pan alley composers), and these guys ripped off previous composers, and society benefited enormously from all of that.
That's something that's all the more apparent today, since something created in one part of the world can be immediately visible worldwide, and won't be forgotten for years. For culture to grow and thrive, you need to be able to rip off, build on, and be inspired by the artists, creators, and inventors that came before you or are your contemporaries. That doesn't happen nowadays.
But the idea itself? You don't deserve to be paid just because you thought about something and put it on paper.
Well, maybe paid a little for putting together previous creators' ideas in a new combination. But in exchange, you have to let other people do the same with yours.
Also, a bizarre but fascinating exploration of perpetual copyright and the future, by Spider Robinson: http://www.spiderrobinson.com/melancholyelephants.html