http://wiki.answers.com/Q/What_was_the_average_income_for_small_business_owners_in_2005
Salary.com did a survey in 2006 of business owners and CEO's salaries. The survey shows that the average income is around $233,000. Note that this salary is in fact under the threshold that Obama would raise taxes on, so Obama will not raise taxes on the average small business owner. Also, this survey defined "small" as having 500 employees or less which is fairly liberal and certainly not what most Americans think of as a small business.
I believe this is incorrect:
I believe its $258,400.
"According to the survey, the national average salary for the CEO/Partner/Owner job function is $258,400"
I also believe Obama's thresdhold is $250k/$200k (Family/Single)
An important note also is that 98.1% percent of small-business filers have income too low to be subject to either of the top two tax rates. Since the floor of these is below $250,000, then 98.1% of small business filers will not see any increase with Obamas plan.
http://www.cbpp.org/8-29-08tax.htm