^^^^^^Here is the answer^^^^^I think it is quite rare and really not much of a hazard. I am certainly not saying go ahead and do it improperly, but I think the risks are overblown. A generator connected in parallel with the live utility will likely just trip the breaker on the genny - I have seen it happen, it was disappointingly uneventful.
A suicide cord is certainly a shock hazard, but I think the chance of injury/fire/death from 120V to ground is quite small per instance, although if you have a few hundred thousand instances, there could be a few.
backfeeding dead utility lines could be a risk for lineman, but I think in most cases the generator would trip out from all the neighbors loads.