That is what I have wondered ever since the boxes started going into standby mode.  The fans still blow, the lights still blink, and the stb is still displaying an image.  The only real difference is the power light goes out.  When I first got UV I realized that the way the dvr could still record programs was because the box never turned completely off.  I woul love to hear what ATT has to say about the effectiveness of their Energy Star initiative.