Canon will offer a hardware modification of the Mode Dial on the EOS 7D and EOS 5D Mark II. From Dec. 8, 2010 in Japan, you can have the Mode Dial replaced with a locking Mode Dial that has a button at the dial’s center to lock the Mode Dial’s setting. Whenever you turn the Mode Dial, you have to first press the button at the center of the dial. The locking Mode Dial is similar to the one found on the EOS 60D.

The cost will be 10,500 yen and you can have it done at any of Canon’s Service Centers in Japan. The modification will take about 10 days in Japan and there is no warranty on the locking Mode Dial. You will have to bear the cost of shipping or taking the camera to a Canon Service Center.

Payment for this modification is required even if the camera still has a valid warranty.

I have the 7D and from my experience, I haven’t had problems with the Mode Dial turning inadvertently. Significant force would be required to turn the dial by accident, but it is possible. This modification may offer peace of mind, but for me, it would be an extra step to turn the dial.

Official Canon announcement in Japanese:
http://cweb.canon.jp/e-support/products/eos-d/eosd-modedial.html