They recently changed those estimates, previously they said that a 10GH/s contract (which in reality is 9GH/s because they keep 10% of the advertised hash rate) would have generated 50BTC in the first year. Those are impossible figures as anybody with a brain would know.
But they reinvest your BTC for more hashing power. I don't know how things are going to work out, but I think the infinite contract holders will make bank. We're the early adopters, the original investors. The ones that put our necks on the line, took the big risk. Time will tell and we shall know soon enough.