In planning my 2012 effort, how do people get their pack on the airplane, check it or as carry-on?

It occurs to me that all my worldly possessions for the next 6 months are going to be in the only piece of luggage I'm taking, my backpack. Do you risk losing it or it being gone thru or stolen by checking it?

What are the carry-on limits? As long as it will fit in the overhead compartment?

Also, I'm thinking there may be a lot of things I want on the hike, like a knife, that would probably get confiscated at the airport, as well as other questionable items, like hiking poles, certain cooking kit items, hygiene items or anything deemed to be capable of being used as a weapon or flammable substance.

Do you just pack your clothes, camping gear(tent, hammock etc.), making your pack as small as possible for carry-on, then go to an outfitter or supply and pick up everything else after you get to Atlanta?