Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Operating activities
Net loss	$ (17,405)	$ (20,771)
Adjustments to reconcile net loss to net cash from operating activities:
Depreciation and amortization	5,651	3,561
Stock-based compensation expense	963	452
Re-measurement of preferred stock warrant liability	(8)	13
Changes in assets and liabilities, net of acquisition:
Accounts receivable	(224)	(62)
Prepaid expenses and other current assets	(1,194)	(833)
Other assets	(150)
Accounts payable	(3,082)	(529)
Accrued expenses	3,562	1,543
Other long-term liabilities	51	57
Deferred revenue	14,546	11,370
Net cash provided by (used in) operating activities	2,710	(5,199)
Investing activities
Purchases of property and equipment	(9,568)	(7,412)
Proceeds from maturities of short-term investments	10,000	6,807
Purchases of short-term investments		(10,069)
Payment for acquisition, net of cash acquired	(1,949)
Net cash used in investing activities	(1,517)	(10,674)
Financing activities
Proceeds from issuance of preferred stock, net of issuance costs		750
Proceeds from exercise of stock options	925	168
Proceeds from issuance of common stock in connection with initial public offering, net of offering costs	55,709
Repurchase of common stock	(22)
Net cash provided by financing activities	56,612	918
Effect of currency exchange rate changes on cash	2	2
Net increase (decrease) in cash	57,807	(14,953)
Cash and cash equivalents, beginning of period	13,855	28,276
Cash and cash equivalents, end of period	71,662	13,323
Non-cash investing and financing activities:
Conversion of preferred stock to common stock	68,858
Conversion of preferred stock warrant to common stock warrant	74
Accretion of redeemable convertible preferred stock	$ 128	$ 158