Ancient cultures broke off pieces of obsidian to make knives and weapons such as arrows.

VOA: special.2009.09.16

Martha Stewart and Emeril Lagasse are being sued for hawking knock-off knives on the Home Shopping Network.

FORBES: Martha Stewart, Emeril Lagasse Hit With Multi-Million Dollar Lawsuit

By Monday afternoon, more than 20, 000 people had signed a petition to WhiteHouse.gov calling on the TSA to keep knives off of planes.

CNN: TSA stands by knife decision

Since the Sept. 11, 2001, terrorist attacks there have been no incidents in which terrorists have successfully used sharp objects to take over a plane, which suggests the current policy of keeping even small knives off planes is working, committee members said.

NPR: TSA Stands By Plan To Allow Small Knives On Planes