I'm about to purchase my first black cab on Friday to start work and having a front facing and passenger facing cam fitted for my own safety in case of any incidents.
As it is a working vehicle I have been advised to get a camera professionally fitted which I am doing. The main difference being that I have no access to the footage it records on a 30hour loop. If an incident occurs and I need to involve the police I then have 30 driving hours to go to the installers in London and only they will access the footage using their software for the police to then view. This way if it goes to court, I cannot be accused of tampering with the footage in any way and the evidence it shows cannot be disputed.
For me, given the nature of my work, it is essential. Might be overkill for a personal car, but definitely food for thought