Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2012

Computation of Basic and Diluted Net Income (Loss) Per Common Share

The following table sets forth the reconciliation of the numerator and denominator used in the computation of basic and diluted net loss per common share for the years ended December 31, 2012, 2011 and 2010 (in thousands, except per share amounts):

	Year Ended December 31,
	2012			2011			2010
Numerator:
Net loss	$	(15,917	)	$	(16,982	)	$	(16,911	)
Effect of revaluation of warrant liability		(2,059	)		0			0
Adjusted net loss used for dilution calculation	$	(17,976	)	$	(16,982	)	$	(16,911	)
Denominator:
Basic weighted average number of common shares outstanding		54,515			48,050			40,300
Effect of dilutive potential common shares resulting from warrants accounted for as liabilities		546			0			0
Diluted weighted average number of common shares outstanding		55,061			48,050			40,300
Basic	$	(0.29	)	$	(0.35	)	$	(0.42	)
Diluted	$	(0.33	)	$	(0.35	)	$	(0.42	)

Anti-Dilutive Effect of Common Shares

The table below presents common shares underlying stock options, employee stock purchase plan rights, warrants, restricted stock units and/or convertible preferred stock that were excluded from the calculation of the weighted average number of common shares outstanding used for the calculation of diluted net loss per common share. These were excluded from the calculation due to their anti-dilutive effect for the years ended December 31, 2012, 2011 and 2010 (shares in thousands):

	Year Ended December 31,
	2012		2011		2010
Weighted average of anti-dilutive potential common shares		8,716		13,595		9,867