Metal detectors on the beach: help or hurt our cleanup efforts?

I've been picking up trash at Ocean Beach in San Francisco every Saturday for about 6 months, and I keep running into this one guy with a metal detector. He digs these little holes and leaves the bottle caps and pull tabs scattered around. Last week I watched him pull a quarter out of the sand and then walk away from a crushed can sitting right next to it. I get that he's looking for treasure, not trash, but those little bits add up. On the other hand, some detector folks do fill their holes and pack out what they find. I've seen a few who even carry a separate bag for garbage. So is the metal detecting crowd a net positive because they at least get people out there, or a net negative because they leave the small stuff? I'm honestly torn. Has anyone else had run-ins with detector users on their beach, and how do you handle it?