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

Wei Kelun wrote:

You guys are both right. If you keep your finger on the AF-ON button in AI SERVO mode while pressing the shutter release, then the camera will indeed try to refocus between shots as the subject moves.

However, if you take your finger off the AF-ON button, then the camera holds the last achieved focus point and will not try to refocus between shots. Taking your finger off the AF-ON button effectively disengages AI SERVO.

This of course is a reason to use back-button-focussing; you don't have the option of disengaging AI SERVO mid-burst if you're using the shutter-half-press to engage the autofocus mechanism. Using BBF gives you a choice about whether you keep the servo engaged, or not.

For what it's worth, I on'y switched to BBF a few days ago (after posting a question about it here) and it's the most intuitive and natural thing ever. I can't imagine going back to focussing with the shutter button.