Skimming through a couple of DAN's annual accident reports, I couldn't find an incident specifically related to whether or not a diver had or didn't have a snorkel. Although fatalities still occurred at the surface, none were described as having anything to do about breathing with a snorkel - or lack or a snorkel - at the surface, but instead being triggered by some other health issue such as cardiovascular disease. Somewhere early in the thread, the idea of a snorkel being "essential" scuba gear was brought up....although not mentioned specifically by DAN, other gear (essential to scuba) malfunctions were.
I think we can put this issue to rest and say that the majority of the SB community replying to this thread (me included), have indicated snorkel use is a personal preference although a few divers may feel it is essential to their diving.
What should have been a pretty easy thread topic to reply to, to wear a snorkel or not, became a little more than that.
"This is how I use or don't use a snorkel and the reason(s) why" should have been sufficient and could possibly help a new diver get a perspective of pros/cons, practical/possible uses, and the type of snorkels/accessories available. Even some of the anecdotes could be helpful if the reader learns a lesson or something new from it.