Middle Class Tax Cut Act of 2011 - Reduces employment tax rates in calendar year 2012 (payroll tax holiday period) for both employers and employees to 3.1%.  Limits the reduction for employers to the first $5 million of wages paid by the employer in 2012. Reduces the tax rate on the first $5 million of net earning of a self-employed taxpayer. Allows nongovernmental employers a tax credit for payroll increases in the last quarter of 2011 and in 2012. Appropriates funds to the social security trust funds to compensate for any revenue loss to such funds from the reduction in rates and the tax credit allowed by this Act. Amends the Internal Revenue Code to impose on individual taxpayers in taxable years beginning after 2012 an additional tax equal to 3.25% of so much of their modified adjusted gross income as exceeds $1 million.  Defines "modified adjusted gross income" as adjusted gross income reduced by any deduction allowed for investment interest.  Provides for an inflation adjustment to the $1 million threshold amount for taxable years beginning after 2013.