The United States Postal Service started a dead letter office in 1825 to deal with undeliverable mail. In 2006 approximately 90 million undeliverable-as-addressed (UAA) items ended up in this office; where the rightful owners cannot be identified, the correspondence is destroyed to protect customer privacy, and enclosed items of value are removed. Items of value that cannot be returned are sold at auction, except for pornography and firearms. The auctions also occasionally include items seized by postal inspectors and property being retired from postal service.
http://en.wikipedia.org/wiki/Dead_letter_office
