The latest news reports, while reporting that Malaysia just admitted (belatedly) that the flight MH370 was carrying lithium batteries in its cargo hold, mention that lithium-ion batteries have caused 140 mid-air incidents in the last 20 years. I didn't know about this. How can the batteries be on fire by itself? How easy? Don't many passengers carry laptops/mobile phones with lithium batteries on airplanes all the time?