My fear as a pessimistic engineer is that unless there is more regulation of HFT, sooner or later someone big (a bank, an exchange, a country) is going to be financially wiped out by a HFT-gone-bad incident, and the resulting mess will take years to unravel while everyone else (pension funds, private investments, etc.) gets to suffer for the sins of their masters.

I propose an exponentially decaying tax on trades - the longer you hold a purchase, the less you pay when you sell it. If you WANT to trade at sub-microsecond levels, you can bloody well pay for the clean-up fund when your system goes bad.