i have to disagree some what with this.
the risk is the person is going to DIE if no oxygen is getting into their body to say there is no benifit to keeping somone alive is silly vs your own risks. yes there is a chance of bodily fluids but you can minimise touching and the risk from the casualty using various methods.
of course every situation is diffrent and you would have to assess it as you find it, you may need to think twice if their on the floor with 3 needles handing out of them but in general the risks shouldnt outway letting somone die surely.

and "JUST" compressions are only good for approx 6mins after you stop breathing.