Mr. Emmerson was a hub in several child pornography trading networks, prosecutors say.
The exchange, a nonprofit membership organization, faces growing competition from electronic trading networks.
The Big Board's halt also crimped fast-growing electronic trading networks like Island ECN and Instinet.
"These trading networks have been around for a long time," Professor Wei said.
Others reckon that slavery made it difficult for the South to establish trading networks.
Their military might, diplomacy, and vast, intricate trading networks commanded deference from European traders, officials, and missionaries.
The increasing use of high-speed Internet connections around the world has spawned vast international trading networks, the authorities say.
The earliest records of extensive trading networks in the world are from the Egyptian, Phoenician, Greek, and Roman civilizations.
Communities of Okinawans sprang up around East and South-East Asia, and trading networks stretched as far as Bengal.
In 2005, both the Nasdaq and the Big Board acquired major electronic trading networks, raising concerns among traders about pricing.
It and about a dozen other companies vowing to build wondrous trading networks were cast aside and left for dead.
