I had another look at the numbers in the B.I.S. preliminary report for 2010 that is available here. By compiling the different tables, I got the following numbers for visible financial transactions in the USA for 2010.
Imposing a 0.1% FTT on that could generate 3 trillion dollars, a value substantially higher than the total US government tax revenue for 2010 which was 2.33 trillion dollars (see table below, compiled from the figures on the IRS website).
Sure, the imposition of the tax would certainly lead to some drop off in activity. But the great thing about FTTs is that you can vary the level every day if necessary to keep the revenue coming in at the required rate.
Increase the FTT to say 0.5% and the US might even be able to pay off its entire national debt (close to $15 trillion) in a year.
Frankly, what's the problem? Why isn't everyone campaigning for an FTT??