Personally, I am leery of bartering with anything that could blow back on me. Butane is fuel, thus explosive. It makes you a target.
I'd much rather trade with convenience items, ie;
hotel soaps/shampoo
TP/wipes
tampons
bandaids
rice/noodle packets
water bottles
laundered used clothing
I am not worried about trading off butane lighters in the least, making something dangerous from it would be possible but not probable. The only real problem I find with storing lighters is that im my experience they like to slowly empty out over time, especially the generic ones. Buy name brand and then rotate them every couple of years and you should be ok.
I like my zippos. Bunch of flints, and you can use all sorts of fuel to light them (though not recommended). Flints are super cheap, and you can store quite a bit of lighter fluid. The lighter fluid ALSO has other uses as well
Full size for me but I keep them and use the Scripto cheapies for barter.
I won't buy any more of those - you may have different experiences, but I bought a few big packages of them and they were all 'dry' and empty withing a year.5-2. About 3-4 years after the cheapies went dry the BICs I bought at the same time still are mostly full.