2. Net Loss Per Share

Basic net loss per share is calculated by dividing net loss for the period by the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing net loss for the period by the weighted average number of shares of common stock outstanding during the period and including the dilutive effect of common stock that would be issued assuming conversion or exercise of outstanding warrants, stock options, share based compensation awards and other dilutive securities. No such items were included in the computation of diluted loss per share in the three and six months ended June 30, 2010 or 2011 because we incurred a net loss in each of these periods and the effect of inclusion would have been anti-dilutive.

Outstanding equity awards not included in the calculation of diluted net loss per share because their effect was anti-dilutive were as follows:


	June 30, 2010				June 30, 2011
	Number of Potential Shares		Range of Exercise Prices		Number of Potential Shares		Range of Exercise Prices
Stock options		6,805,743	$	0.47 - $16.36		7,254,690	$	0.47 - $16.36
Unvested restricted stock awards		1,645,920	$	—		2,303,779	$	—
Warrants		1,602,489	$	2.40		1,602,489	$	2.40