Tom Vanderbilt in Slate:
“When backing in, I have to drive past the slot, then back in. On my way past it, I can look in the slot to ensure it is clear. I have situational awareness, so it is pretty safe to back in. When I leave, I just have to drive out and that is safer than backing out. If I don't back in, when I leave I have to back out into what is basically unknown traffic.”
Backing into traffic in parking lots is more hazardous than you might think. Parking lot crash statistics are a bit hazy, particularly for crashes involving only property damage, but a study by the Insurance Institute for Highway Safety in 2001 and 2002 found that 14 percent of all damage claims involved crashes in parking lots (some number of which must have involved vehicles moving in and out of spaces). More seriously, there is a whole category of crashes, often fatal, tracked by the National Highway Traffic Safety Administration, called “backover crashes“: These typically occur in driveways and parking lots, often involve children, and happen at a higher rate to drivers of SUVs and “light-duty trucks,” owing to the reduced visibility they offer (not just to their drivers but to those parked adjacent). Indeed, the last crash I was involved with occurred when a driver backed his SUV from a parking space into my driver's side door as I waited for traffic to clear. The driver said he never saw me, even though our cars were only a few feet apart, and it's almost certain the crash would not have happened had the driver employed “back-in, head out” parking.
More here.