[Updated] A few of our readers have noticed MetroCard vending machines fare collectors* on the Upper East Side. Situated outside a Duane Reade on East 86th Street and First Avenue, the two MetroCard fare collectors, plus a coin fare collector, are part of the Select Bus Service for the M15.
Select Bus Service is being implemented to speed up bus rides. The buses will have dedicated bus lanes (maybe) and will be equipped with three doors for quicker boarding and exiting. Tickets will be sold at sidewalk kiosks; riders will also be on the honor system and not required to show their tickets unless asked—scofflaws will be subject to a $100 fine!
There's already SBS on the Bx12, and that's been a success.
Update: As readers pointed out, these are not vending machines but fare collectors. You insert your MetroCard into the MetroCard fare collector (or put change in the coin fare collector) to pay for bus service and get a receipt—which is your proof that you're allowed to be on the bus.