[Luis Guerrero]"I would like to know when it is acceptable in situations other than on an ENG assignment."
When the scene directions, talent or director call for a "boom mic to be visible in the shot" for comic effect or to show (in the scene) that this is a "staged" or "news" event.
I can't think of any other time it SHOULD be there.
Otherwise, you wouldn't NEED a boom, as the talent could simply hold a hand mic or wear a lav.
In general, a boom in the shot is normally "bad form."
Think of it as seeing a stagehand dressed in blue-jeans standing near the edge of the frame of a scene that is supposed to be on the surface of the moon.
It instantly breaks the mood of the moment as it screams "this is a MOVIE" (and a poorly-produced one, as well).
I would agree that there aren't many times in which seeing a boom is acceptable. On something like that show Insomniac with Dave Attell on Comedy Central, I think it is. I think it has to be a very loose form type show for it to be that acceptable though, but not in movies unless for comedic effect.