You know, then again, I guess it depends on the way you want the item found.
If I want visitors searching for "Haleakala National Park" I might want to do this: haleakala-national_park
That way I get them if they use just "haleakala" and if they include the "national park" on the end.
"Greatness is not a function of circumstance. Greatness, it turns out, is largely a matter of conscious choice, and discipline." - Jim Collins