[Sapph]

There's another company that lets travelers subsidize their flight ticket / earn money for delivering US products to their destination:

https://grabr.io/travel

Key difference is:

You buy the products locals ordered (locals pay for item + delivery fee upfront into escrow) so there's no risk of a third party hiding drugs or illegal materials.

[uiri]

One risk is if the item is perfectly legal and ordinary in the US but is illegal to import into the foreign country. The courier could wind up paying heavy fines or much worse.

Kinder eggs are an example of an item that is perfectly fine in, say, Canada, but carries a heavy fine for import into the US.

[inertial]

Evading duty is still a legal issue. Some countries have laws that permit you to carry some articles without duty, for personal use. This is a clear subversion of such rules.

[DrJaws]

This is an amazing idea that works, not the airmule one.