I think they just tend to error on the side of "customer is always right".
I had a refurb Macbook pro Core Duo that had the expanding battery problem - fortunately within warranty. The took one look and immediately pulled out a new battery and gave it to me.
Happened again out of warranty, and no AppleCare. Again, new replacement battery with no fuss.
Then I gave away the machine to a friend, and he had the 3rd battery fail via expansion. His apple store did the same - new battery, no fuss.
Now, one could argue that maybe the batteries shouldn't be failing after, but I feel like they're treating me fair, and won't feel bad about buying their products in the future. Heck, I go to the apple store over other retailers now - rather give my money to them.
Other than the battery issue (and the iPhone that got dropped in the toilet), all my apple equipment has been very reliable. You don't have to appease customers as often if you don't screw up.