A Tobin Tax is generally meant by a tax on foreign exchange transactions, which have historically remained untouched. Although not the user fee on all transactions that we talk about here, the Tobin Tax is a good model for investigating the feasibility and success of such a fee.
There have been concerns raised with how to implement such a thing, but as Brazil has shown, it can be done, and just this March, Canada also passed a Tobin Tax measure.
Joseph Stiglitz: Supports Tobin Tax -- So it's OK for banksters to collect it on international transactions, so it should be OK for Americans to collect it on the banksters, I say.
Pete DeFazio has a bill -- Not without detractors -- I learned from that link that there used to be a tax on all stock trades: "The United States imposed a transfer tax of 0.2 percent on stock trades between 1914 and 1966."