Remove card quickly?

At the gas station, you insert your debit/credit card and are advised to “remove card quickly”. What happens if you don’t? Other merchants, like Kinko’s, the credit card machine sucks in your AMX card and holds it until you have finished your laptop/printing/internet session. Why the difference?

I encounter plenty of other swipe card readers, although most of them are the “swipe across the slot at the top” sort. Safeway has them, for example. In fact, I would say I see far more swipe readers than motorized ones. I would WAG that it’s mostly a cost issue. Swipe readers are probably cheaper. The gas pump is a vertical surface, so they incorporate the “insert and remove card” reader rather than the swipe reader you see sitting on a countertop.

It asks you to remove card quickly becusae it is reading the card on the way out rather then on the way it when you are still stumbling to get it sliding correctly.

It specifies quickly not because anything bad will happen if you don’t, but rather because on those types of readers the stripe data is read upon removal of the card, and moving the card faster across the read heads produces a more reliable signal than pulling it out slowly. This is mainly because when you pull slowly, it might tend to move the card across the head in a nonuniform manner; consistent speed is the key to good data reading.

If you are on treadmill and pull the card out at the speed of light … ?

This is correct. The “insert and remove” type and the “swipe” type readers both have no moving parts, which are therefore cheaper and are more reliable in the long term (if there’s no motor, the motor can’t break). There are disadvantages to these as well. They can’t capture and keep a stolen card like a motorized unit can. Also, since they rely on you to pull or swipe the card at a constant speed, they are more prone to errors. Swiping quickly or pulling the card out quickly forces you to move at a more constant speed, which helps to reduce these errors. The signal processing in the swipe and remove types is also more complicated. In the motorized type, the motor always moves at the same speed, so the data coming off of the card is always in the same place. With hand moved cards, the data can come in faster or slower, depending on how fast you physically move the card.

If you are having trouble getting the machine to read your card, you can try pulling it out slower, but (as QED already said) you want to keep the speed as constant as possible.

Here’s some links if you want to know what’s on that little magnetic stripe:

(warning - pdf)

But the “remove quickly” aspect seems unique to “dip” (That’s the in-and-out type, as opposed to the “swipe” readers where you slide the card through a slot.) readers on gas pumps. I don’t recall ever seeing “remove quickly” on an ATM with a dip reader.

No cite, but ISTR articles about cash machines and the like swallowing cards that are left in them too long as a security measure.

Yup, card capture is a feature implemented in many ATMs.
Less and less, recently, as ATMs get cheaper and we see more units, especially the kind you see inside of retail locations, that have dip readers.
Incidentally, I recall at one point that the ATM operator, be it a bank or other entity, could get paid a hefty bounty for capturing a cancelled card. Apparently the banks were glad to have ‘bad’ cards out of circulation due to the associated fraud risk. I seem to recall a ‘capture’ reward on the high side of $100.
I don’t know how that works currently.

I remember the first time I used a card to buy gas. I was kind of leary, fearing my account would be somehow mangled. When remove card quickly came up on the screen, I kinda panicked. I thought I was the only one getting that message.

Assuming there is a particular reason for that message, I guess it would be because most people’s instinctive reaction when the card reader doesn’t read their card is to try it again, but more slowly. This makes sense when speaking to someone, but as Q.E.D. explained, it’s probably worse when using a card reader.
So the message specifies ‘quickly’, in order to avoid this common error.