Gas, even more expensive than you thought

Using your debit card at the pump can be more of an expensive hassle rather than a convenience. I learned this a while ago but was just unsure of how it works. Basically the minute you swipe your card at a prepay pump, the gas station's computer talks to the bank's computer to authorize -- or freeze -- a sum of money. When you swipe your debit card, the gas station is legally able to put a hold on your account, sometimes up to as high as $100. This enables the gas station to confirm a valid bank account. But the hold can remain on your account for a few days. Even if you were to purchase only a few gallons worth of gas, you could have a hold on your bank account for around $100. If you only have a few hundred dollars in your account, this could cause you serious grief later on. This is benefiting the gas company but is hurting the consumer. How many people using their debit cards are actually aware of this going on? My guess would be not very many. If the company is allowed to do this, it seems like a warning or disclaimer should be in place to inform the consumer about what is going on.