It's the only satellite radio provider, but this isn't such a big advantage now that nearly all of its customers already pay for mobile internet service.

The major market indices may have hit fresh all-time highs this week, but Sirius XM Holdings (NASDAQ: SIRI) investors weren't invited to the party: Shares of the satellite radio provider hit a 12-year low this week.

Berkshire Hathaway owns 31% of Sirius XM Holdings, the satellite-radio company, and one of Berkshire’s investment managers also holds an interest in the company.Berkshire held 105.2 million shares of Sirius XM as of Sept.