There are two points of view with regard to the use of helmet mounted cameras.  

It could be argued that obtaining the footage following a crash would make it is easier to assess liability.

However it has also been said that the cameras are not aerodynamic, which could result in riders being fatigued by uneven weight distribution; exposed to sudden wind gusts, especially large vehicles passing in the opposite direction.

Therefore, if considering a helmet-mounted camera, please ensure that you take into account the pros and cons before purchase.