A few years ago, back during my senior year of high school on a school trip to Italy, a guy on the trip had his spit cup on every single bus trip during the 2 weeks. On one particularly hilly area near Sorrento, the cup went flying into the aisle. Possibly one of the most disgusting things I've ever experienced (as well as everyone else on the bus).

I can see this easily happening on a bumpy flight which would ruin my flight like it did the bus trip (the driver didn't clean the bus till the next day). I've luckily never encountered someone dipping on a flight with me, but DL has the right plan -- no tobacco -- period. CO should consider the rule.