How the hell does anyone determine that? If someone walked out of Id during Quake III development with Carmacks's inverse square root (http://stackoverflow.com/questions/1349542/john-carmacks-unu...), would that be a trade secret? It's not like an inverse square root is a secret, but what about doing it faster than anyone else?? Writing the best 3D engine was part of their success, and writing the fastest order routing/exchange is a big part of HFT. He took source code from GS to go to a competitor that had offered him a lot of money, it's hard to have much sympathy for the guy.