Magnets in Apple Laptops; How does this work?

It's pretty well established that magnets cause problems with technology. Credit cards, MP3 players, and computers are all supposed to be kept distanced from them. So how is it that Apple managed to put magnetic power cord ports and magnetically closing screen lids on their laptops without damaging the computers? This seems counter-intuitive to me. Why would a company known for making a quality product put something inside that could potentially damage its contents?