Specialist vs. Generalist Debate

In running a business and/or building your career, you're likely asked to choose one of two tracks: to become a specialist or to pursue the path of a generalist.

1. Under what conditions do you prefer being a specialist or generalist (or some type in the middle or even a new type of preference if any)? Please provide sufficient details to support your arguments.
2. Please describe, predict, and justify how a preference between being a generalist vs. specialist (or some type in the middle or even a new type of preference if any) would or should look like in the next five or ten years (e.g., ratio changes over time). To be feasible, you can address this question by focusing on a chosen scope (e.g., a narrowed and in-depth one vs. a broad and big picture), perspective, domain, time span (next 5 years vs. next 15 years).