This excerpt taken from the SIRI 10-Q filed Nov 12, 2008.
Higher than expected subscriber acquisition costs could adversely affect XMs financial performance.
XM is spending substantial funds on advertising and marketing and in transactions with car and radio manufacturers and other parties to obtain or as part of the expense of attracting new subscribers, including its subscriber acquisition costs and costs per gross (or net) subscriber addition. XMs ability to achieve cash flow breakeven and profitability within its expected timeframe or at all depends on its ability to continue to maintain or lower these costs, which vary over time based on a number of factors. If the costs of attracting new subscribers are greater than expected, XMs financial performance and results of operations could be adversely affected.