1. The act of routinely coming up with ideas on the spot, especially when under pressure or with a high penalty for failure. This derives from the vaunted ability of journalists and reporters to generate news story ideas with unexpected or novel angles. This term is a logical progression from the phrase "to pull an idea out of my ass". Used as a positive term of praise, a "butt miner" is somebody who is very good at thinking of new ways to cover old stories, or of new stories that nobody else has thought of before.
2. This could also conceivably be a term for a sodomite (or possibly a proctologist) or anybody else who spends a fair amount of time in a butt. But I've never heard this term used that way.
Reporter: "Hey, I have an idea. Instead of just covering Chinese New Year at the restaurants, why don't we cover the plight of the Chinese staff at the restaurants, who have to work the festival and who can't go home to their families in China?"
Editor: "That is a compelling idea with a human angle, and a novel way of covering a routine annual event. A sterling display of vintage butt mining. Good job!"
Reporter: "I love Katie Couric. I really admire her bravery in having her own colonoscopy broadcast on TV."
Reporter: "Aye. That's a sterling display of vintage butt mining, no doubt."