Stock Incentive Plan (Tables)

9 Months Ended

Sep. 30, 2013

Stock incentive plan

Summary of activity under the Company's 2008 Stock Plan, including grants to non-employees and restricted stock issued

The following table summarizes activity under the Company’s 2008 Stock Plan, including grants to non-employees and restricted stock issued (in thousands, except per share amounts):

	Shares Available for Grant		Options Outstanding		Weighted Average Exercise Price per Share		Aggregate Intrinsic Value
Balances at December 31, 2012	347,386		2,227,669		$	2.06	$	4,311
Additional options authorized	250,000		—		—
Options granted	(636,654	)	636,654		4.70
Options exercised	—		(324,892	)	1.46
Options forfeited	183,852		(183,852	)	2.69
Balances at September 30, 2013	144,584		2,355,579		$	2.81	$	21,928
Vested—September 30, 2013			1,217,163		$	2.02	$	12,290
Expected to vest—September 30, 2013			2,234,726		$	2.77	$	20,904

Summary of outstanding and exercisable stock options

Outstanding and exercisable stock options at September 30, 2013 are summarized as follows:

	Options Outstanding		Options Vested and Exercisable
Exercise Price	Number	Weighted-Average Remaining Contractual Life (in Years)	Number	Weighted-Average Remaining Contractual Life (in Years)
$0.08	177,750	4.89	177,750	4.89
$0.80	196,194	6.40	178,718	6.39
$2.36	430,134	7.06	328,880	7.06
$2.40	216,875	7.94	141,416	7.95
$2.68	653,952	8.53	282,438	8.51
$4.00	473,299	9.33	107,961	9.32
$6.04	198,375	9.72	—	—
$7.92	9,000	9.94	—	—
$0.08-7.92	2,355,579	8.02	1,217,163	7.28

Schedule of assumptions used to calculate estimated grant date fair value of employee stock options using the Black-Scholes option-pricing valuation model

	Three Months Ended September 30,		Nine Months Ended September 30,
	2013	2012	2013	2012
Weighted-average volatility	80.57%	84.33%	80.42 - 81.41%	83.06 - 84.33%
Weighted-average expected term (years)	6.08	6.08	5.0 - 6.08	5.0 - 6.08
Risk-free interest rate	2.11%	0.75%	0.88 – 2.11%	0.75 - 1.19%
Expected dividend yield	0%	0%	0%	0%

Stock-based Compensation

Stock incentive plan

Summary of share-based compensation expense

Stock-based compensation expense recognized was as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
Cost of revenue	$	10	$	5	$	23	$	21
Research and development	67		38		170		86
Selling and marketing	46		29		123		81
General and administrative	238		96		535		270
Total	$	361	$	168	$	851	$	458

Equity-based Compensation

Stock incentive plan

Summary of share-based compensation expense

	Three Months Ended September 30,				Nine MonthsEnded September 30,
	2013		2012		2013		2012
Cost of revenue	$	—	$	1	$	—	$	2
Research and development	—		27		—		71
Selling and marketing	—		10		—		31
General and administrative	—		39		—		99
Total	$	—	$	77	$	—	$	203