As someone has mentioned before the likes of the NYSE, by having access restricted to brokers, have the luxury of not having hoards of amateurs jumping on trends at whim causing the kind of peaks in demand the Betfair system is designed to handle. ....
most internet based trading systems allow ordinary users to place orders on NYSE or ARCA
orders are executed based on prices @ NYSE , almost instantly (a few seconds lag if at all)
in this internet and computing age, I see the absence / presence of a broker as a hindrance rather than boon
IMHO
regards