The key to 'unlimited' services is that the rate at which most users accrue stored data is slower than the rate at which storage becomes cheaper. That is to sa

The key to 'unlimited' services is that the rate at which most users accrue stored data is slower than the rate at which storage becomes cheaper. That is to say, in the time it takes for your data to go from 1 GB to 10 GB, their cost-per-GB has gone down by >90%.