Condensed Statements of Cash Flows (Unaudited) (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Cash Flows from Operating Activities:
Net loss	$ (13,127)	$ (7,239)
Adjustments to reconcile net loss to net cash used in operating activities
Loss from disposition of assets	1	3
Stock-based compensation	1,439	2,147
Non-employee stock option expense	6	(11)
Depreciation expense	253	287
Amortization of investment premiums	46	119
Issuance of common stock for services rendered	25	1
Changes in operating assets and liabilities:
Accounts receivable		4,410
Prepaid expenses and other current assets	58	(997)
Accounts payable, accrued expenses and other liabilities	107	3,704
Deferred revenue		(9,854)
Net cash used in operating activities	(11,192)	(7,430)
Cash Flows from Investing Activities:
Purchases of available-for-sale securities	(1,025)	(8,309)
Proceeds from maturity of available-for-sale securities	16,585
Decrease in restricted cash	102	103
Purchases of property and equipment	(21)	(79)
Net cash provided by (used in) investing activities	15,641	(8,285)
Cash Flows from Financing Activities:
Proceeds from exercise of common stock options and employee stock purchases	43	71
Payments on capital lease	(8)	(10)
Net cash provided by financing activities	35	61
Net increase (decrease) in cash and cash equivalents	4,484	(15,654)
Cash and cash equivalents, beginning of period	17,008	25,471
Cash and cash equivalents, end of period	$ 21,492	$ 9,817