Meet Sirius XM’s new odd couple: Warren Buffett and John Mayer

Warren Buffett, the famed investor, and John Mayer, the popular songwriter and guitarist, would seem not to have much in common. But one thing they both share is a big bet on Sirius XM Holdings Inc. SIRI, -1.47%,the satellite-radio company.  Buffett’s interest comes via Berkshire Hathaway Inc.’s BRK.A, -0.73% BRK.B, -0.70%position in Liberty Media Corp.’s Series A LSXMA, -1.09%and Series C LSXMK, -1.27%tracking stocks for Sirius XM, which represent the value of a port