A couple of years ago, I was busy gawking at a yard sale while out riding and I ran into the back of a pickup truck that had stopped behind a car turning left on a four lane road, with parked cars on either side.
My fault entirely.
And I'm absolutely positive that similar incidents happen to cyclists, novices and experts alike, everywhere. One moment spent staring at the Powertap or at a skipping rear derailleur, and you can pile right into some immovable, hard object.