Bolstered by a report suggesting that too much salt can be a factor in stomach cancer,

and

shaken by the suggestion that 6 cups of coffee could prevent diabetes in men.  After much sniffing around, I did discover that in the Netherlands, where this study was done, that number of cups equates  28 oz, not the 48 or more some people are mentioning.  Even so, that is a LOT of coffee, and the whole thing is very mysterious.  One report says 

"More than 4,200 reported drinking at least seven 125-milliliter cups (about four ounces each) of coffee a day. These people were fatter, less active, smoked more and ate worse than those who drank less coffee. Yet their risk of developing Type II diabetes was half as high as that of men and women who said they drank two or fewer cups of coffee a day."

The researchers themselves suggest the possibility that other ingredients such as antioxidants or magnesium may be involved - we will just have to wait and see. The one thing I have not been able to find out is whether the coffee was black, or contained milk and/or sugar.  I think that would be relevant, but no source I can find mentions it.