I know of at least two places with piles and piles of pallets. They also have a very large chipper and make hardwood woodchips all day long. They won't let you have any of their pallets :) Kind of like the old days of reusing pop bottles, the economics of companies collecting and reusing pallets for anything other than local shipping type uses is not great. There is more value getting (or possibly paying) a couple of pennies from someone who collects them and turns them into woodchips. As a hobby I find some satisfaction in the reuse of pallet wood. I don't really consider the few minutes (or in some more difficult situations many minutes) of time and effort expended as a "cost" any more than I figure my time into the "cost" of some little box I build. If I did, and given how long it takes me to build anything, I would never make anything because it would "cost" too much. Far "cheaper" to go sit on my ass and watch TV :-) (of course I could charge myself for TV watching too)
Basically, if you enjoy "found wood" and the process of getting and taking pallets apart and seeing what little treasures you can find then go for it. If it seems a chore and an effort and you would rather buy some wood at the local lumber yard or mill and spend more time actually building, then leave the pallets for others or for the woodchippers.
Dave Hall