I have accidentally touched so many breasts I can't count anymore. How? Have a baby, then hand it off to every female friend you have. They are so worried about the newborn's neck, etc, that you can't help but cop a feel basically every time you hand the baby over. And a few times my hand has actually been caught between the baby and a friend's breast to the point where I had to speak up to get my hand back. Totally true.
I have never touched on purpose, though, but I haven't gone out of my way to not touch, either.