I was watching recordings of a nature program on Smithsonian last night. I think the recordings were made before the HD/SD issue. Anyhow, those programs were not letterboxed for me, but rather picture-framed. I checked the channel I was on and indeed it was the HD version. It's not just Smithsonian that does this crap; many channels do this on their SD subchannels, for instance. Rather than making it widescreen in SD, they letterbox it first. Then when a widescreen TV gets it, it's picture framed. 
