5. Stock-Based Compensation and Employee Benefit Plans

Stock-Based Compensation

The Company uses the Black-Scholes valuation model to calculate the fair value of stock options and employee stock purchase rights granted to employees. The Company calculates the fair value of restricted stock units based on the fair market value of our Class A common stock on the grant date. The weighted-average grant date fair value per share of the restricted stock units granted in the three months ended March 31, 2012 was $5.51. No restricted stock units were granted during the three months ended March 31, 2011.

The fair values of stock options and employee stock purchase rights were estimated at their respective grant date using the following assumptions:

Stock Options

The risk-free interest rate assumption was based on the United States Treasury's rates for U.S. Treasury zero-coupon bonds with maturities similar to those of the expected term of the award being valued. The assumed dividend yield was based on the Company's expectation of not paying dividends in the foreseeable future. The weighted-average expected life of options was calculated using the simplified method as prescribed by guidance provided by the SEC. This decision was based on the lack of relevant historical data due to the Company's limited historical experience. In addition, due to the Company's limited historical data, the estimated volatility incorporates the historical volatility of comparable companies whose share prices are publicly available.

The Company recognized stock-based compensation in the statements of operations as follows:

Employee Benefit Plans

2010 Equity Incentive Plan

The 2010 Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock unit awards, stock appreciation rights, performance-based stock awards, and other forms of equity compensation, or collectively, stock awards. The exercise price for an incentive or a non-statutory stock option cannot be less than 100% of the fair market value of the Company's Class A common stock on the date of grant. Options granted will generally vest over a four-year period and the term can be from seven to ten years.

On January 1, 2012, 1,329 shares of Class A common stock were automatically added to the shares authorized for issuance under the 2010 Plan pursuant to an "evergreen" provision contained in the 2010 Plan.

2010 Employee Stock Purchase Plan

The ESPP is implemented through a series of offerings of purchase rights to eligible employees. Generally, all regular employees, including executive officers, employed by the Company may participate in the ESPP and may contribute up to 15% of their earnings for the purchase of the Company's common stock under the ESPP. Unless otherwise determined by the Company's board of directors, Class A common stock will be purchased for accounts of employees participating in the ESPP at a price per share equal to the lower of (a) 85% of the fair market value of a share of the Company's Class A common stock on the first date of an offering or (b) 85% of the fair market value of a share of the Company's Class A common stock on the date of purchase.

On January 1, 2012, 415 shares of Class A common stock were automatically added to the shares authorized for issuance under the ESPP pursuant to an "evergreen" provision contained in the ESPP.

Common Stock

At March 31, 2012, the Company had 500 million authorized shares of Class A common stock and 500 million authorized shares of Class B common stock. Holders of the Company's Class A and Class B common stock have identical voting rights, except that holders of Class A common stock are entitled to one vote per share and holders of Class B common stock are entitled to ten votes per share with respect to transactions that would result in a change of control of the Company or that relate to the Company's equity incentive plans. In addition, holders of Class B common stock have the exclusive right to elect two member of the Company's Board of Directors, each referred to as a Class B Director. The shares of Class B common stock are not publicly traded. Each share of Class B common stock is convertible at any time at the option of the holder into one share of Class A common stock and in most instances automatically converts upon sale or other transfer.