Have you ever thought of placing cash inside of an envelope and sending it across the globe? There are places around the world where one will find strict economic controls on their people or have problems with crime. As such, sending money to friends and family becomes a dangerous and/or difficult process. For example, if your friend was in dire need of money and the only way of getting it to him was to place cash in a box and ship it to a specific location, would you? If you decide to do so, be careful.
If Customs and Border Protection (Customs)/Homeland Security seizes your cash when transported through Express Consignments (i.e. FedEx, UPS, DHL) you will likely find that the alleged violations are of 19 U.S.C. §§ 1481, 1484, and 19 C.F.R. Part 128. Further, Customs will reason that you misdescribed currency/monetary instruments in express consignment shipments. If this occurs you will be facing administrative forfeiture proceedings. A seizure notice will be issued to the sender and recipient of the package.
It is best to consult an attorney experienced in Customs matters at that point as a poorly planned strategy may end up leaving your cash forfeited to the United States government.