Still annoys me though that such a cheap game (and now with a demo too) is being pirated in the first place. But then, seeing what happened to World of Goo, just goes to show that there are some real *******s out there.
World of Goo still managed to climb to the top spot of Amazon's PC sales charts, above things like Spore or WoW. PC sales are on par with the game's Wii sales (if not better), so they don't seem to be doing that bad. And lots of other people playing the game I see as a good thing - if I were given the choice between a 1,000 sales and 10,000 players or 1,010 sales and 1,010 players, I'd go with the former.
As for Defense Grid, the game's nice, but overpriced. You could actually get a proper game for 20$ (hell, even three, if you're looking at GOG), instead of a simplistic tower defense game, of which already exist countless free variants. It's a whopping zero bucks they're going to see from me, unless they halve their price - whether I also pirate the game or not is a separate matter.