As the title suggests, I have ignored the rule of not buying and playing Minecraft and I now play it often... and it's great! Really, really good and I can't believe how good it is... The way that the map you play on is randomly generated (mine's called "Brave New World"), the fact that you can do anything you want with no constraints and that your friends can come into your world and help you build that amazing skyscraper you had plans to build or you could go into their world and blow their house up by inviting some creepers to stay ;)
So far, I have built a mine-shack that is next to a mine I have dug with the finding of iron, coal, gold and redstone being one of the best experiences in gaming. Near to this is my main house in the middle of a body of water with a bridge of sand joining from all directions at the front of the house... and I'm proud of it! That's why Minecraft is so great; it takes the idea of crafting and if you put the effort in, you can create some truly amazing pieces of art/architecture.
I must go, "Brave New World" calls me.