How David's Friends Became A Force for Good and Not Evil

I am listening to Dakota Oak - with Malcolm Mooney reading Rip Van Winkle. Because it is Malcolm from CAN it becomes an event. If it was Junior Senior it would be a shrug. And was just thinking: When does guest stars on albums detract or add? I've never been a fan of Eddie Vedder but his voice rings in admirably on the new Cat Power like methodone withdrawal clinic graffiti. Heartbreaking and sad. What occurrences add? What subtract?