The thing to understand is that HFT is a forced, private tax by the parasites against the real economy.  By imposing a 1% tax on transactions legitimate business would be benefited as the HFT wouldn't be allowed to occur.  And if the HFT moved into the shadow banking system who would they be sucking off of?  They can't simply all suck off each other as HFT is reliant upon the real economy to provide its 'host capital'.  A shadow trading exchange without a Tobin Tax (after it was implemented) would be so filled with HFT that no legitimate trader would touch it.