bk - As for the "hold charge"... Hotels do it all the time, and it's usually worse. They are legally able to put a hold on the full amount of your stay when you check in, and that hold does not fall off your account until a couple days after you check out. -Although, some credit card companies will take off the hold when you call them. *I actually keep a separate credit card for that purpose - I use it for check-in - then when I check out, I give the front desk another card to put all the room charges on. This way I don't have a "ghost" double charge temporarily depleting my funds.
As for gas stations... They used to put a hold of $0.01 on your account - basically to make sure it was a real, active card. However, with the current gas prices - and the rash of pump-and-go drivers - they've had to authorize larger amounts. And they are apparently well within their rights - and your rights - to do that. I saw a few news stories on it last year when the practice started.
As mentioned, going inside to have your card swiped is a "better" way to pay for your gas when using a credit card. The other option is to use a Debit card.