this company operate similar with speedrent...
but frankly speaking... credit card can exceed credit limit, and be cancelled anytime... to me it is just another marketing gimmick to tell the owner... "Why use an agent, and pay them commission, whereby you can do it all yourself"
there is no right or wrong on this, if you only have one property and have the luxury to monitor your rental of each room on a monthly basis, I do think it is a great idea.
For people who have many properties, I do think they want to reduce all these hassle not to mentioned they have to perform their own client filtering and due diligent that is normally being done by a professional real estate negotiator.
It is a free world at the end of the day.