So if I understand correctly for any block of data it will be stored on at least two separate hosts. The hosts have to be "always-on and connected with a business-class Internet account". So in essence you are using another 2 companies datacentres to store your block of data. So far, so resilient. But suppose these two companies are actually using the same physical data centre (not impossible in our ever-consolidating world), then you potentially have a single point of failure. Or am I being a Monday morning grump?