You can't buy more than one MetroCard at MetroCard vending machines in the same day using the same credit card.

It's not that they tell you so explicitly, but if you try to buy a second MetroCard before the day is out, you get a mysterious "Temporarily unable to process payment" message.

Now, what's the point of this? To save us from our own excess?

This limitation is particularly vexing if you're, say, trying to purchase MetroCards for a group of folks, say, out-of-town visitors.

If you happen to have a Visa or MasterCard debit card, though, I've discovered that you can successfully make two purchases a day. Select the option to use it as a credit card one time and as a debit card the other.

Of course, you can use cash at token booths as many times a day as you want, but that's not the point. Token booths (increasingly misnamed since tokens have just been phased out) are not always open or convenient, but that's not really the point. The point is trying to control the number of MetroCards going out into consumer's hands and not advertising the limitations on the system. A person depending on being able to purchase more than one MetroCard could find himself stuck, for not understanding the limitations.