The whole point of having a laptop is its mobility, right? I once flew across the country for a job interview and realized after I arrived . . . that I was charger-less with none at the front desk. Sure, there was no shortage of Apple stores to replace it, but I couldn't justify the price for something I already had (in working condition) at home.
Moral of my story: When packing any item that uses a power source, double check that said power source is packed, too.