Employee Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2012

Employee Benefit Plans [Abstract]

Amounts recorded as expense in the consolidated statement of operations

	Three Months Ended June 30,				Six Months Ended June 30,
	2011		2012		2011		2012
Cost of revenue	$	59	$	104	$	123	$	151
Technology and development		67		79		134		137
Sales and marketing		104		136		213		224
General and administrative		345		796		729		1,162
Total	$	575	$	1,115	$	1,199	$	1,674

Summary of weighted-average fair value of stock options granted

	Three Months Ended June 30,				Six Months Ended June 30,
	2011		2012		2011		2012
Stock options granted (in thousands)		32		79		138		871
Weighted average fair value at date of grant	$	6.42	$	5.46	$	6.09	$	5.35

Stock option activity

	Shares			Weighted average exercise price		Remaining contractual term (years)		Aggregate intrinsic value (dollars in thousands)
December 31, 2011		4,540		$	7.29		6.62	$	10,888
Granted		871			9.69
Exercised		(8	)		1.00
Forfeited		(160	)		7.86
Outstanding as of June 30, 2012		5,243		$	7.68		6.72	$	38,665
Vested and expected to vest at June 30, 2012		4,451		$	7.62		6.31	$	29,845
Exercisable at June 30, 2012		4,196		$	7.32		6.07	$	28,690

Calculated fair value of option award using the Black-Scholes option pricing model

	Three Months Ended June 30,		Six Months Ended June 30,
	2011	2012	2011	2012
Fair value of underlying stock per share	$12.10	$10.66	$10.98 - 12.10	$9.59 - 10.66
Expected volatility	54.72 - 54.77%	54.63 - 54.75%	54.72 - 56.09%	54.63 - 56.14%
Risk-free interest rate	2.18 - 2.23%	0.95 - 0.98%	2.18 - 2.72%	0.94 - 1.74%
Expected term	5.90 - 6.07 years	5.94 - 6.08 years	5.47 - 6.08 years	5.27 - 8.50 years
Dividend yield	—  %	—  %	—  %	—  %