Just saw another smart person release something under the GPL. I really, really need to get my act together and write up a single, coherent paper on how this hurt free software. I've started a couple of times (mostly in e-mail discussions), but never completed it.
Overall conclusion: The GPL only makes sense if you hate commerical software so much that you are willing to hurt free software to hurt commercial software, if you love gratifying your own ego more than you love free software, or if the building blocks you are using force you to use the GPL. There is a long buildup of economics to show this, something I was surprised at when I first discovered it.