For instance, if I knew the producer of certain items, I might decide to buy directly from them instead of through a middleman, such as a grocery store, but now there are all kinds of barriers to doing just that. Furthermore, if I could somehow contact the coffee farmer who grew my coffee beans, then I could also ask him for a particular kind of bean that I might prefer. This is less efficient in the production sense than shipping everything in large batches, but might be more efficient in the sense of getting what I want. It is quite common when shopping for furniture to find exactly what you want, except too wide, narrow, high, etc. Having it hand-made in the west would be prohibitively expensive, perhaps 10x of the price of the item, so we settle for the one which is not quite right. But if there was a simple mechanism for ordering the modified item from the original developing world producer then that might be very useful.
I guess the question is not whether we could make marketplaces more visible to better know whom our elves are. The question is whether we want to.
I love that even while stating this, there's still some bias creeping in. It could just have likely been a hard-pressed farmer whose children go educated in your country, or from some other country that treats their farmers better than your own.
Your concluding statement about this knowledge affecting your choices would probably be a nightmare for these retail giants who might fight tooth and nail to stop this.