Will disconnecting the power supply to an HDTV on a regular basis cause it any harm?

The problem is this. If you unplug or diconnect the power supply immediately after running the television it will harm the TV. However, if the television has been off for an hour so, it will not hurt it. The reason is that when you power off a television, the cooling fans still run for a while, cooling off the televisions internal components. However, if you disconnect the power supply immediately after running the TV, it also cuts off the Fans....this extra heat contributes to problems late on.

DEFINITELY. Don't make the same mistake I made. I saved up for ages for a HDTV (dont remember name). I kept disconnecting like that and the quality began to get poorer and poorer. Eventually the display was so dark, I couldnt see anything and had to get rid of it. It's also impossible to fix the problem.

On some sets, one never knows, but a Bravia hopefully has a properly sized power supply with Japanese electrolytics and respectable build quality. If the power supply WERE to fail, it's definitely repairable, thankfully... unless it takes something with it when it goes, that is.

it won't hurt it to remove AC.