Why is the Apple logo upside down when the lid is open on the older Apple notebooks?
A former Apple employee, Joe Moreno has a blog post explaining why:


  "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."


So when closed, it appeared right-side up from the point of view of the user. But when opened, it appeared upside down from the perspective of on-lookers. Joe Moreno states that "Opening a laptop from the wrong end is a self-correcting problem that only lasts for a few seconds. However, viewing the upside logo is a problem that lasts indefinitely."

All of these decisions of course went through Steve Jobs. With the release of the current Macbook product lines, Jobs reversed his decision and had the logo appear right-side up from on-looker's perspective.

Sources:

Upside Down Apple Logo - 
http://blog.joemoreno.com/2012/05/upside-down-apple-logo.html

The Upside Down Apple Logo: A Steve Jobs Mistake - 
http://www.cultofmac.com/168377/the-upside-down-apple-logo-a-steve-jobs-mistake/