The official name for this beverage is Dieci the Italian for 10 and is the brainchild of The Pulp & The Bean coffee shop in Brooklyn. Owner Tony Fischer is quoted in the US press saying: "This is for the person who wants to experience the limits of where coffee and espresso can go."
We've worked out that the 20oz drink equates to one gram of caffeine. For the record, caffeine intoxication is said to take place after drinking in excess of 250mg in one go. However, 10g of caffeine is known to be the 'lethal dose' that would reportedly kill 50% of people. So you could easily down a cheeky second cup on the way to work, assuming you can handle the side-effects of diuresis, cardiac arrhythmia and 'psychomotor agitation'.