This excerpt taken from the SIRI 10-Q filed Nov 12, 2008.
Weaker than expected market and advertiser acceptance of XMs radio service could adversely affect XMs advertising revenue and results of operations.
XMs ability to generate advertising revenues will depend on several factors, including the level and type of penetration of its service, competition for advertising dollars from other media, and changes in the advertising industry and economy generally. XM directly competes for audiences and advertising revenues with traditional AM/FM radio stations, some of which maintain longstanding relationships with advertisers and possess greater resources than it does, and new media, including Internet, Internet radio, podcasts and others. Because XM offers its radio service to subscribers on a pay-for-service basis, certain advertisers may be less likely to advertise on its radio service.