My household ahs had HD service via Direct TV for six months, and one of the interesting quirks in the low percentage of HD ads that run during HD programming.
I've read trade articles about the aesthetic choices that must be made for ads that are to be served across broadcast networks, and they are valid choices that must be made. I've had the same discussions on virtually every new project that is shot 16:9 but won't be seen by the every viewer in that aspect. It seems that most projects have multiple destinations, so you must 4:3 protect while still making the 16:9 image interesting anyway.
But I'm surprised that only half of the ads on Discovery's or ESPN's HD feeds are also HD. The reduction in viewer experience is dramatic. If I'm an advertiser who has paid for access to an HD stream, I would want the maximum impression.
I understand there is an added expense to posting in HD versus SD, assuming the content originated on film or in HD, but when you factor in the cost of production and editing in relation to the cost of the ad buy, I see value in spending the extra dollar on the front end to maximize the impression on the back end.
That's why the "free" ad a TV station will produce in exchange for an ad buy are expensive in bad viewer impressions. You get what you pay for.
I imagine this will become less of an issue as the DTV conversion happens, but I am curious how long the residual issues will evolve.