I wouldnt regularly do it at 100yds with a 30/30 but with most "deer rifles" (243s and up) the result is you better get your skinnin knife out! I love a neck shot because they typically produces a "down right now" effect and dont damage meat like a true shoulder shot. A straight on lungs (no shoulders) will equally kill but rarely is the fall immediate. I shoot tough bullets (Xbullets, Fail Safes etc) for many reasons and one is that when shot in the neck the exit hole isnt large enough to cause alot of work for the taxidermist and "surgery charges". I also encourage their use because sometimes that "all you get". How many times have you heard, "He stopped behind the brush and all I could see was his head". Well to me that sounds like someone isnt as proficient with their gun as they should be. If you saw his head you had all the vitals you needed. Drill em right behind the ear (where the skull ajoins the spine) and its simply OVER. When presented with a full neckshot I prefer to shoot them at the base of the neck just ahead of the brisket.

Deer hunting is already a low odds game, why make those odds worse by waiting for a shot that might never be presented?
RA