I Guess that all depends on whether you trust the service disconnect to actually disconnect all ungrounded conductors.
As far as I am concerned, If I trust it to protect me on the load side, I believe it will protect everyone on the line side.
I do believe it has to be a special circumstance that even allows back feeding the grid. My thought is when the average homeowner generator hits the locked rotor of a neighborhood full of air conditioner and refrigerator compressors the generator will kick out or burn up.
That is plenty of reason to insure you are transferring the load tho.
