A new survey by Frank N. Magid Associates reports a stunning and terrible problem with many Americans' understanding of hi-definition television. The Magid group claims that 43 percent of HDTV owners don't subscribe for hi-def service -- in many cases, the study suggests, because they don't know that they own a hi-definition set. Wait -- it gets worse. Thirteen percent of respondents say that they've never even heard of high definition. If true, that would mean 39 million Americans are completely oblivious to the glories of HD programming. Is this a tragedy? A cataclysm? I don't know. I'm not a poet or a paleoclimatologist. But it does put life into perspective.