1) When your camera isn't built to handle it.
2) When there's no good RAW workflow software for your files.
3) When you're short on storage space.
When RAW adds little or nothing
1) When quality takes back seat to throughput.
2) When you're in control of the light... and you know you won't print big.
3) When you're a total newbie to digital post-processing.
Ken's Objections
KO1: "RAW is for tyros. Pros get it right the first time."
KO2: "RAW wastes your time."
KO3: "RAW takes up space."
KO4: "RAWs are unsuitable for archival."
KO5: "RAW looks no better than JPEG."
KO6: "You can't send RAWs to your clients."
KO7: "Different software opens up the files differently."