Its all well and good having them for evidence of other peoples idiocy, but if you have it on recording all of the time (and you'd want it running all of the time automatically 'just in case') what happens if you make an error yourself? Especially if you're the sort of driver who likes a good hoon every now and then - and lets be honest, most of us here would probably be guilt of that...

Capturing someone elses mistakes is all well and good but I wouldnt want anything to provide any evidence for the prosecution should I make my own error of judgement!