When I reviewed the Panasonic TC-PVT50 series I was annoyed to see that the latest software update caused a banner ad to appear whenever I turned on the TV. It disappeared quickly and only popped up upon power-on, but it was still obnoxious. The first thing I wondered was whether I could turn it off.
Happily, Panasonic built in a way to disable the advertising. It's a simple, albeit buried, menu command. Here it is in a nutshell.
The VT50 review sample I tested also has an ad on the main VieraCast home page. Unfortunately there's no way to remove or disable it (the option is currently grayed out on the home page customization screen), but at least it's less annoying than the banner.