Stockholders' Equity (Tables)
 12 Months Ended
Dec. 31, 2016
Equity [Abstract]  
Stock Option Activity Related to Shares of Common Stock
The following table summarizes stock option activity related to shares of common stock (in thousands, except weighted average exercise price):

 
Number of
stock options
outstanding
 
Weighted-
average
exercise
price
 
Weighted-
average
remaining
contractual
life (years)
 
Aggregate
intrinsic
value
Outstanding—December 31, 2015
2,168

 
$
6.48

 
5.20
 
$
118

Granted
1,010

 
3.47

 
 
 
 
Exercised
(2
)
 
3.20

 
 
 
 
Forfeited
(1,029
)
 
7.07

 
 
 
 
Outstanding—December 31, 2016
2,147

 
$
4.79

 
6.35
 
$
8

Options vested and expected to vest—December 31, 2016
1,418

 
$
5.32

 
5.32
 
$
7

Options exercisable—December 31, 2016
773

 
$
6.39

 
3.44
 
$
4
Summary of Stock Options Outstanding
The following table summarizes information regarding stock options outstanding at December 31, 2016:

 
Options outstanding
 
Options vested and exercisable
Exercise prices
Number of
stock options
outstanding
 
Weighted
average
remaining
contractual life
(years)
 
Weighted
average
exercise price
per share
 
Shares subject
to stock options
 
Weighted
average
exercise price
per share
 
(in thousands)
 
 
 
 
 
(in thousands)
 
 
$2.12-$3.09
216

 
9.53
 
$
3.04

 
5

 
$
2.12

$3.25-$3.27
280

 
9.30
 
$
3.26

 
—

 
$
—

$3.74-$3.74
350

 
9.25
 
$
3.74

 
—

 
$
—

$4.14-$4.14
147

 
8.38
 
$
4.14

 
58

 
$
4.14

$4.30-$4.30
308

 
4.80
 
$
4.30

 
143

 
$
4.30

$4.42-$4.66
179

 
6.61
 
$
4.60

 
60

 
$
4.58

$5.07-$5.07
294

 
3.90
 
$
5.07

 
191

 
$
5.07

$5.58-$5.84
226

 
2.30
 
$
5.66

 
172

 
$
5.66

$6.01-$17.94
128

 
1.20
 
$
11.92

 
125

 
$
12.02

$18.80-$18.80
19

 
0.68
 
$
18.80

 
19

 
$
18.80

$2.12-$18.80
2,147

 
6.35
 
$
4.79

 
773

 
$
6.39
Restricted Stock Award and Restricted Stock Unit Activity
Restricted stock award and restricted stock unit activity is summarized as follows (unit numbers in thousands):

 
Number of
units
outstanding
 
Weighted
average grant
date fair value
per unit
Awarded and unvested at December 31, 2015
329

 
$
4.40

Granted
543

 
3.52

Vested
(190
)
 
4.05

Forfeited and canceled
(242
)
 
4.01

Awarded and unvested at December 31, 2016
440

 
$
3.69
Fair Value of Option Awards
The fair value of the option awards was calculated using the Black-Scholes option valuation model with the following assumptions:

 
Year Ended December 31,
 
2016
 
2015
 
Expected term (in years)
6.0

 
4.9

 
Risk-free interest rate
1.40
%
 
1.37
%
 
Expected volatility
57
%
 
47
%
 
Expected dividend rate
0
%
 
0
%
 
Cost of Net Revenues and Operating Expenses Include Stock-Based Compensation
Cost of net revenues and operating expenses include stock-based compensation as follows (in thousands):

 
Year Ended December 31,
 
2016
 
2015
 
Cost of net revenue
$
49

 
$
163

 
Sales and marketing
269

 
300

 
Technology and development
81

 
180

 
General and administrative
1,208

 
1,063

 
Total stock-based compensation expense
$
1,607

 
$
1,706