I hate that button. I've lost a lot of the feeling in my hands and can't easily operate buttons. In 14 years of using DSLR's. I've never had the dial turn by accident. I wonder what it might cost to heve it removed
I bought my first 5DMKII in '08 and have two plus a MKIII. I have NEVER turned the mode dial by accident on either MKII. I don't know if I hate the button on the MKIII, but to me it is definitely more of a hinderance than a help. I would definitely prefer the camera without it.
I do a lot of photography on the move... with the camera hanging from my shoulders by the straps, mode dial issues were ALWAYS a problem for me... I would have the dial on M or AV and bring the camera up ready to shoot and next thing I knew it could be in B or C1 or whatever and if i was lucky, i would catch it before I did a shot and got burned... if I wasn't, I would lose shots. First time I ever really had that problem.. 50D, didn't catch the problem... lost an entire shoot. My camera usually goes whereever I go and that mode dial has always been a liability for me... not anymore...
Canon 5d III, Canon 24-105L, Canon 17-40L, Canon 70-200 F4L, Canon 100L 2.8, Canon 85 1.8, 430EX 2's and a lot of bumps along the road to get to where I am.