Stupid question. What kind of game have you ever downloaded that cost the developers EXACTLY $0 in time and effort to provide that game?
You probably meant "$0 to them for me to download or copy the bits." But I don't see the point in ignoring the very real costs incurred by the developer in the honest hope of compensation for that labor.
I also get irritated by people (not just you, but others in this thread and legion on the internet) that consider the right to pirate software and entertainment a great human right worthy of moral outrage. I might understand someone tempted to steal health care through some sort of fraud if they can't afford it legally, or justify stealing food or shelter or some basic necessity of human life. But defending the right to steal entertainment (most of it pretty low artistic quality to begin with) is just kind of pathetic and not worth the time expended. You must feel some sort of need to justify your own moral misgivings if you're taking time out to rationalize the virtues of pirating content, when you could be spending that time more productively in finding other content to pirate.
Again, this is not aimed at you, specifically, but also all of the people on Reddit, Slashdot, and Digg who spend so much time coming up with these rationalizations. I have more respect for the people who just pirate and don't claim it as some moral crusade against the Evil RIAA and Friends.
$20 is cheap too. If you can't afford $20, get a better job. Or spend the time you would have devoted to playing World of Goo teaching yourself the skills to get a better job. Again I'm not perfect but I can't justify stealing a $20 game from an independent developer. Stealing a tv show or $2000 software might be a gray area, but World of Goo deserves support.