Fair Value Measurements

6 Months Ended

Jun. 30, 2012

Liabilities, Fair Value Disclosure [Abstract]

Fair Value Measurements

Fair Value Measurements

Generally accepted accounting principles set forth a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. The three tiers are Level 1, defined as observable inputs such as quoted prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions.

Our preferred stock warrants are measured at fair value on a recurring basis. The preferred stock warrants are valued using the Black-Scholes model with the following assumptions: share price, exercise price, expected term, volatility, risk-free interest rate and dividend yield as described in “—Note 11—Redeemable Convertible Preferred Stock”.

Changes in valuation during the years ended December 31, 2011 and the six months endedJune 30, 2012, were as follows:

	Level 3 Warrant Instruments
Balance, December 31, 2011	1,150
Mark-to-market adjustment	169
Balance, June 30, 2012	$	1,319

Mark-to-market adjustments related to stock put options and warrant instruments are included in other income (expense).