It is not rare to be in this particular situation. Really, you are not At Fault, but you still shouldn't get angry at the other vechicle's driver.
Another View: Not enough information is given in the question. If the other car was stopped and waiting for you to back out and YOU ran into THEM, YOU are at fault.
If both cars were in simultaneous motion (they were pulling in while you were backing out) BOTH parties are at fault. One for not yielding and the other for backing without caution.
both of you for not looking back
You are at fault.
Backing up--it is your fault.
In most circumstances, the backing vehicle has the greater duty of care and would be found at fault.
Most likely the the vehicle doing the backing up would be at fault.
A vehicle traveling in a parking lot has established use of the lane and the right of way. A vehicle in a parking space and backing into the lane must yield to oncoming traffic. Therefore, if a vehicle is backing out of a parking space and pulls into the path of an oncoming vehicle that has already established the lane, the vehicle backing would be at fault for the accident. However, if the vehicle which established use of the lane had an opportunity to avoid hitting the vehicle backing out of the space and failed to do so, there could be comparative negligence on both vehicles or on the one who had the opportunity to avoid the accident.
The backing vehicle is at fault. We are always supposed to look to ensure the path is clear before placing our vehicle in motion.
the car backing out.
Any time the driver who is backing is at fault, in all 50 states.
no matter where a vehicle is parked, the moving vehicle is at fault every time.
The vehicle exiting the parking space that did not yield to oncoming traffic.
The vehicle that was performing the backing maneuver is generally always the one at fault.