2. Who knows what chemicals are left behind on the sticker.
4. Stickers get toss into the garbage. Or worse if you are eating on the run just littered.
There are no chemicals. The stickers are made of starch, are printed on with edible dyes and are stuck on the fruit with a thin layer of glucose. They are in fact perfectly edible and biodegradable. It's quite possible laser etching (by heating the fruit) will produce more dangerous compounds. Frankly, this isn't even a problem, people just like the lasers because they look cool.
"What a wonder is USENET; such wholesale production of conjecture from such a trifling investment in fact." -- Carl S. Gutekunst