I think that's why Xbox Live arcade games have been so successful. Each and every game is a downloadable demo that gives you a real taste of the full version and then immediately gives you the opportunity to purchase it while still playing the game while the proverbial iron is hot. The PC and Xbox 360 are probably the best at this, followed by PS3. The Wii doesn't offer them and it suffers because of it (at least my purchases). The iPhone and similar mobile app stores also tend to offer lots of lite versions to entice you and/or very low cost of entries (.99 is hard not to take a chance on). It makes perfect sense, just like longer song demos on sites like iTunes and Amazon MP3.

I'm still trying to figure out how to place mined blocks in Minecraft. I played my full version for the first time yesterday and was of course killed by monsters once night fell and I didn't build a shelter...