There is little value in having the credit card number of an account that has too little activity to charge. It almost deterred me and when I recommended Bluemix to a friend, this is one of the first things he mentioned. I had to reassure him that he will not come close to the thresholds while in development. Parse.com does not ask for a credit card. It allows you to just jump in. This is very attractive to a scrappy startup that has no idea what load he will place on a Paas service.