1. Howard Stern signs a new three-year contract with SiriusXM. 2. Berkshire Hathaway increases its stake in SiriusXM by 4% recently. 3. SiriusXM has 33 million paid subscribers but faces competition. 4. Stern's audience is vital; 2.7 million may cancel without him. 5. SiriusXM's advertising revenue increased to $455 million last quarter.