If you do a quick google search on 'cracked macbook display', you'll find many forums with users who have had this exact problem. For example:
http://www.macworld.com/forums/ubbthreads/showflat.php?Cat=0&Number=439503&Main= 422824
Here's my 2cents.
Had the macbook for 3 months now, and I LOVE it.... But I was carrying it upside down yesterday and felt an ominous crack. When I opened it there was a hairline fracture which has grown considerably since. There is no evidence of physical damage on this unit. I keep it in a case whenever I carry it. There are no dents, dings or scratches of any kind on it. This computer is my baby. I am an electrical engineer, and am trained in dealing with technology; I have at least 3 different laptops in my house and 2 desktops. I have never ever had an issue with a cracked screen up until now.
When I took it to the Apple store the "Genius" was very rude even after I explained the situation and basically called me a liar. When I asked to speak to the manager she did not budge one inch, and basically just listened to my complaint and regurgitated what the other guy had said. There are plenty of other forums, even on the Apple website, that deal with this same complaint. I plan to call apple customer support later today and in addition to explaining my situation, file a complaint against the manager and "Genius", who were basically laughing at my misfortune. If this does not work out, I plan to file a complaint to the Massachusetts comsumer authorities under the lemon law. There is no way a company should be able to sell a product for this much money with a defect that costs this much to fix.
MacBook Mac OS X (10.4.7)