Apparently some MacBook Pro batteries are swelling out of their case. A while back, I've read a post by some IT hardware support guy blaming swollen battery for a MacBook with touchpad button stuck in down state. I thought the post was bogus at the time but now I am not sure.
My guess is that most of MB and MBP problems are due to the unusually high temperature pushing all hardware components into the edge of their spec. Simply put, I wouldn't expect an iPod used in Siberia or Sahara desert to last as long as one used in California. But then I've noticed that electonic goods don't last longer than a few years these days where they used to last nearly a decade with only minor problems. My first VCR lived on for a little over 10 years and was still operating (with some wise nudging and toeing) when I replaced it another which lasted only two years before breaking down completely. Expenses don't bother me much but the chore of shopping sure does.