You are correct that just as many buyers as sellers do not understand the meaning of COD however if a buyer wants out of the deal for any reason they can insist on cash on delivery and if the seller does not comply they are very likely to leave neg feedback, trash the DSRs and perhaps even earn the seller a defect if they complain to ebay.

Personally I have never understood how anyone could imagine something that starts with a D, for delivery, could mean a different word altogether that starts with a C as in collection.