There were a non-trivial number of people wearing these in the Incheon, Bangkok, and Penang airports though none from the Dulles to Incheon flight. (Does this say something about the (ir)rationality of Asians?) My mom almost made us get some in Penang until she found out that they were sold in packs of 100. My only real concern was trying to keep the kids from touching their faces (noses, mouths) with their hands after touching all kinds of things in the plane and the airport.
Thankfully, no mishaps so far.