Those wanting to put a newer hd tv in front of a window, this is actually fine the old rule of don't put a TV in front of a window was mainly for old tube TVs, like consoles and earlier TV's because the hot sun would over heat the tubes and cause them to shatter like when a light bulb gets too hot. There is still only two main issues you would have to worry about like discoloration, however most TV's now are made of a plastic that resists discoloration. The other may be that it could possibly overheat and melt some of the soldering inside but again they do have protection for that because general use heats the TV up to around 80 to sometimes 120 degrees possibly higher depending on the room temp, and where you live. So in all honesty newer TV's made after 2007 should have no issues really, the discoloration can happen from about anything but it would take about 15 years and most people don't keep TV's that long anymore. As for over heating I wouldn't worry much the main thing you will need to worry about in my opinion is dust. Windows tend to attract dust like magnets and you're TV creates a lot of static electricity which attracts dust, so in all as long as you keep up on cleaning it, dusting it and so forth then it should be fine.
Also if it does get a bit hot there is things you can do, the instructions say a operating temp but most TV's will operate over that on their own I don't think you have much to worry about but as a added note you can do more damage if you put the tv directly across from a window which WILL damage the screen.