Well, since we're back discussing this again, I will concede one advantage with the Metrocard. That is when you buy a $10 card, they give you one extra ride, or $12 worth. Not a bad deal after all. But I still say tokens were simple and effective, and you didn't find old ones scattered on the floor around stations either...........
And one other thing. A friend of mine bought a brand new Metrocard and it wouldn't work. Employees in the booth ran the card though their computer or whatever it is, and said it was an empty used card. This was 5 minutes after he bought it brand new from the machine! We didn't have this problem with tokens either.............
Now whenever I buy any fare card or train ticket from a machine, I always get a receipt too, just in case of another such fiasco.