I don't think the presence of helmet cameras alone will make much difference to the way motorists treat cyclists. Firstly as I believe the vast majority of dangerous manouvers are due to the motorist failing to understand the cyclists requirements rather than them thinking they can get away with putting the cyclist at risk. Secondly today's helmet mounted lights look very similar to cameras and I believe the lights are more common and motorists (inc myself) have become wise to this and will be unaware of a camera when a cyclist has one as they will assume it's a light.
However, I believe the reporting/sewing/broadcasting culture, if it continues to grow, will have a long term positive effect on the way motorists treat cyclists as motorists will know what they could face and as a result will hopefully incorporate more safety margins into their manouvers involving cyclists. A camera is required to facilitate this.
As it happens I have recently purchased the cheapest 170 degree camera that I could find from
eBay knowing that if it's a load of s**t then I won't be disappointed. Early observations are that it would provide suitable means of settling a claim in day light however I am yet to test it in the dark but I think it will be a "get what you pay for" result.