You are comparing me managing a few shares to Julian Assange and Kim Dotcom, seriously?
Just offering examples of US laws having power outside the US. In response to the excerpt I quoted.
Like I already said, you're brokerage service likely won't be big enough for law enforcement to go after.
... In addition, foreign broker-dealers that, from outside of the United States, induce or attempt to induce securities transactions by any person in the United States, or that use the means or instrumentalities of interstate commerce of the United States for this purpose, also must register. This includes the use of the internet to offer securities, solicit securities transactions, or advertise investment services to U.S. persons. See Securities Exchange Act Release No. 39779 (March 23, 1998)
http://www.sec.gov/rules/interp/33-7516.htm.
How hard is it to add "Service not available to US citizens" to your conditions?