Does the 7D Refocus Every Frame in an 8fps Burst?

Jeff is right. If you're in ONE SHOT mode, then the camera will not refocus between shots. The camera will focus when you press the shutter half-way down (or when you press the AF-ON button if you're a committed back-button focusser), and then when you hold the shutter button down there will not be any refocussing. All the shots in your 8 fpm burst will all be focussed at the same distance.

In AI SERVO mode, the camera will initially focus as above, but then it will attempt to refocus during the burst. This will slow the burst down somewhat, depending on how much work the camera has do to between shots.

Just for fun, I tried using the manual focus ring to make my own human version of AI SERVO, with me as the servo. The advantage would be refocussing on a moving target at full 8 fps with no slowdown of the burst. The disadvantage is that it's bloody difficult to focus with the viewfinder blinking like a seizure-inducing strobe light.