yes, but having each company start their own chain[...]
Who said anything about
each company starting their own chain? That's not distributed, nor decentralized.
The future of satoshi's proof-of-work technology is a chain marketplace. Multiple chains will exist for different purposes (bitcoin, BitDNS, BitX). Multiple chains will exist in the same competitive space (bitcoins, jgarzik-coins).
Wall Street firms may cooperate on a single "Wall Street NASDAQ chain", where all NASDAQ stocks are traded, for example. That would be cooperative and super-strong, yet secure against double-spending (aka naked shorting, etc.)