Some textures (such as dirt) are rendered as black when they have transparency. On the other hand, others don't (such as grass top). This is a major exploit, as people can run texture packs with invisible block textures, which allows them to see through terrain and easily find things they shouldn't be able to (secret bases, spawners, ores, etc.). I propose that non-transparent blocks (not glass, for example) be rendered as black when the texture is transparent.