9. Additional Paid-in Capital


		Warrants		Stock options and RSUs		Compensation options		Other paid-in capital		Total additional paid-in capital

As of December 31, 2010	$	10,721	$	4,695	$	-	$	7,565	$	22,981
Convertible notes broker warrants		(336)		-		-		336		-
Warrants exercised		(97)		-		-		-		(97)
Compensation options issued		-		-		588		-		588
Stock options exercised		-		(430)		-		-		(430)
Stock options expired		-		(828)		-		828		-
Stock options amortization		-		1,496		-		-		1,496
Restricted stock units exercised		-		(392)		-		-		(392)
Restricted stock units expensed		-		524		-		-		524
As of December 31, 2011		10,288		5,065		588		8,729		24,670
Warrants exercised		(601)		-		-		601		-
Warrants issued		3,260		-		-		-		3,260
Warrants expired		(11)		-		-		11		-
Stock options amortization		-		1,081		-		-		1,081
Stock options exercised		-		(50)		-		50		-
Stock options expired		-		(1,585)		-		1,585		-
Restricted stock units expensed		-		3,144		-		-		3,144
Compensation options exercised		-		-		(294)		294		-
As of December 31, 2012	$	12,936	$	7,655	$	294	$	11,270	$	32,155

Warrants

Warrant activity is summarized in the following table:


	Warrants outstanding		Valuation		Weighted average exercise price per share	Weighted average remaining life (yrs.)		Intrinsic value

As of December 31, 2010	16,138,480	$	10,721	$	3.48	4.6	$	57
Convertible notes broker warrants expired	(200,000)		(336)
Exercised	(88,242)		(97)
As of December 31, 2011	15,850,238		10,288	$	3.91	3.7	$	485
Exercised	(619,565)		(601)
Expired	(10,871)		(11)
Issued (Note 8)	4,757,941		3,260
As of December 31, 2012	19,977,743	$	12,936	$	4.25	2.6	$	-

The 19,977,743 outstanding warrants expire in the following time frames: 2,666,666 expire July 2014, 2,091,275 expire December 2014, and 15,219,802 expire in October 2015.

The fair value of warrants issued during 2012 was estimated at the issue date using the Black-Scholes Merton fair value model adjusted to relative fair value using the following assumptions:


Expected volatility	63.70%	-	67.50%
Risk-free interest rate	0.24%	-	0.26%
Expected life (years)	2
Dividend yield	N/A

Compensation Options


	Compensation options outstanding		Valuation		Weighted average exercise price per share	Expiry date	Weighted average remaining life (yrs.)

As of December 31, 2010	-	$	-	$	-
Issued	450,000		588		3.30	April 2013	2.0
As of December 31, 2011	450,000		588		3.30	April 2013	1.3
Exercised	(225,000)		(294)
As of December 31, 2012	225,000	$	294	$	3.30	April 2013	0.3

Stock-Based Compensation

Under our Stock Option Plan (the “Plan”) and our Long-Term Equity Incentive Plan (the “LTIP”), we may grant options and/or restricted stock units (“RSUs”) or restricted stock awards (“RSAs”) to our directors, officers, employees and consultants. The combined maximum number of our Common Shares that may be reserved for issuance under the Plan and the LTIP is a variable number equal to 10% of the issued and outstanding Common Shares on a non-diluted basis. Options under the Plan are granted from time to time at the discretion of the Board of Directors of the Company (“Board”), with vesting periods and other terms as determined by the Board. The LTIP is administered by the Board, which can delegate the administration to the Compensation Committee of the Board or to such other officers and employees of Vista as designated by the Board. Stock-based compensation expense for the years ended December 31, 2012, 2011 and 2010 is as follows:


		Year ended December 31,
		2012		2011		2010

Stock options	$	1,081	$	1,496	$	382
Restricted stock units		3,144		524		126
	$	4,225	$	2,020	$	508

As of December 31, 2012, stock options and RSUs had unrecognized compensation expense of $314 and $3,589, respectively, which is expected to be recognized over a weighted average period of 0.74 and 1.76 years, respectively.

Stock Options

A summary of option activity under the Plan as of December 31, 2012 and 2011 and changes during the period then ended is set forth in the following table:


	Number of options		Weighted average exercise price per option	Weighted average remaining contractual term		Aggregate intrinsic value

Outstanding - December 31, 2010	2,588,661	$	3.55	2.90	$	463
Granted	1,246,000		3.04
Exercised	(354,984)		2.48
Cancelled	(85,500)		3.44
Expired/Forfeited	(199,177)		6.90
Outstanding - December 31, 2011	3,195,000		3.27	2.73		1,039
Granted	600,000		2.97
Exercised	(32,500)		2.90
Expired	(660,000)		5.19
Outstanding - December 31, 2012	3,102,500	$	2.80	2.68	$	637

Exercisable - December 31, 2012	2,802,500	$	2.79	2.49	$	626

A summary of our unvested stock options as of December 31, 2012 and 2011 and changes during the period then ended is set forth in the following table:


	Number of options		Weighted average grant-date fair value per option

Unvested - December 31, 2010	82,500	$	1.36
Granted	1,246,000		1.60
Vested	(693,000)		1.57
Forfeited	(38,000)		1.51
Unvested - December 31, 2011	597,500		1.60
Granted	600,000		1.47
Vested	(897,000)		1.56
Unvested - December 31, 2012	300,000	$	1.47

The fair value of stock options granted to employees, directors and consultants was estimated at the grant date using the Hull-White Trinomial lattice option pricing model using the following assumptions:


			Years ended December 31,
	2012			2011			2010

Expected volatility	81.69%	-	83.67%	83.40%	-	83.86%	81.86%	-	82.88%
Risk-free interest rate	0.77%	-	0.88%	0.88%	-	1.60%	1.51%	-	2.88%
Expected life (years)	5			5			5
Dividend yield	N/A			N/A			N/A

Option pricing models require the input of highly subjective assumptions, including the expected price volatility. Expected price volatility is based on the historical volatility of our Common Shares. Changes in the subjective input assumptions can materially affect the fair value estimate. The expected term of the options granted is derived from the output of the option pricing model and represents the period of time that the options granted are expected to be outstanding. The risk-free rate for the periods within the contractual term of the option is based on the U.S. Treasury yield curve in effect at the date of grant.

Restricted Stock Units

The following table summarizes the RSU activity under the LTIP as of December 31, 2012 and 2011 and changes during the years then ended is set forth in the following table:


	Number of units		Weighted average grant-date fair value per RSU

Unvested - December 31, 2010	175,500	$	2.37
Forfeited	(10,000)		2.37
Vested	(165,500)		2.37
Granted	960,000		3.84
Unvested - December 31, 2011	960,000		3.84
Cancelled	(107,832)		3.07
Granted	1,142,339		3.20
Unvested - December 31 , 2012	1,994,507	$	3.52

A portion of the RSU awards vest on a fixed future date provided the recipient continues to be affiliated with Vista on that date. Other RSU awards vest subject to certain performance criteria, including the accomplishment of certain corporate objectives and the Company’s share price performance. The vesting of all RSUs is at least one year.