9to5 Mac has gone on record as saying that the rumored Apple Brick isn't a product, but a manufacturing process that can make high quality aluminum shells. The "brick" part comes in because the supposed technique carves these MacBook casings with lasers and high pressure water jets out of bricks of aluminum, making for a seamless and screwless design. Whether or not it's true is still left to be seen, but one benefit would mean that there would be no need to bend metal (which creates weak spots). Again, no idea if this is legit, but 9 to 5 Mac has a fairly decent track record, which they conveniently point out at the end of their post. [9 to 5 Mac]
Update: Apple's previously stated that they found a company in China to manufacture their iMacs out of a single piece of aluminum. So, assuming the rumor isn't 100% accurate, this could be a new process with the same company to make MacBooks in a similar way, or Apple found a way to do this themselves with a in-house plant.