Some of Apple's employees were and decided to ask the question for themselves and we given the following answer:
We were told by the Apple design group, which takes human interface issues very seriously, that they had studied the placement of the logo and discovered a problem. If the Apple logo was placed such that it was right side up when the lid was opened then it ended up being upside down when the lid was closed, from the point of view of the user. [...]
Why was upside down from the user’s perspective an issue? Because the design group noticed that users constantly tried to open the laptop from the wrong end. Steve Jobs always focuses on providing the best possible user experience and believed that it was more important to satisfy the user than the onlooker.
We're happy to say they Apple finally reversed it's decision, and turned the logo around which I think looks much better when I'm catching up on all my Facebook happenings while sipping on an Earl Grey at me local cafe !!