I bought my Macbook November 2006 it was cracking over the IR port by June 2007 and I got it replaced. Now in April 2008 its cracking again. It has a very short life. It's almost timed down to a tee when its going to crack. My friend bought one at the exact same time and it has cracked for the second time at the same time. My brothers got his replaced in september and he bought his macbook in April.
I think its crazy.I think Apple should be required to replace this part every time this happens to a consumer. They are building disposable laptops that are almost deigned to break after a specific period. But don't get me wrong I love apple - but it is some shoddy design in this product.