I've had a front facing dashcam for a couple years. I was considering getting a rear, but getting the wires and setting it up back there proved to be a major hassle. The front facing one will probably absolve me of most things - i.e. it will show that I wasn't at fault. So, I figured there was not point. I've been seriously reconsidering it though.

While the front camera can absolve me of wrongdoing, the rear camera would be a better since it would show things to incriminate other people. I've had countless experiences in the last 2 years alone where super aggressive people with road rage got inches away from rear ending me. And it's not just the threat of being rear ended, but it shows context in case they do something even more extreme like swerve around me and cut me off.

The front camera only shows a little. It won't show the person swerving in and out of lanes behind me before side swiping my car as they try to get around. A side swipe can easily end up with a 50/50 ruling. But a rear camera showing them recklessly driving would certainly absolve me of any liability.

The front camera also won't show someone texting on their phone while they tailgate me.

I was driving on an expressway in New York City last month. Out of nowhere, 4 cars flew by me, inches away from causing a collision, easily going 120+ mph. They were racing and swerving in and out of lanes. I checked my footage and my front camera wasn't able to get their license plates since they were only in range of my front camera for a quarter second. I would have got them had I had the chance to record them approaching.