Reliability and robustness are features of ThinkPads, not basic laptop functionality. With the ThinkPad, a good chunk of the 2.5k goes towards making it a solid product. With the apple, a good chunk goes towards making sure it's pretty and a trendy product. Simple as that.
Must have been before they were bought by Lenovo. Seems like the T61's we have at work are nothing but trouble.
Regarding the new Macbooks, the casing machined from a solid block of aluminum is very robust. Quite a bit more robust than any Thinkpad I've ever had by hands on.