Our scheme does have some limitations as compared to existing Internet backup services. Perhaps the biggest limitations are the limited grace period (2 weeks) and the need for sizable amounts of predictable Internet connectivity. Unlike the existing services, which provide long grace periods (months if not years) and only require a computer to be connected to the Internet when a snapshot needs to be saved, our scheme leaves computers with no backup at all in case of excessive downtime. Unlike schemes based on off-line media, our scheme offers little protection against catastrophic viruses that suddenly erase most PCs' hard drives.
Also, our scheme is somewhat less convenient than the best Internet backup services: we provide no tech support line to hold users hands and will not Fed Ex a CD copy of a user's data to them so they don't have to wait for a restore over a slow Internet connection. Depending on the uptime-level agreement, restoration may take longer in our scheme than with the existing services. In theory, Internet backup sites could offer insurance (``if we lose your data, we'll pay you a million dollars''). Insuring users in our system seems problematic due to possible fraud using the disrupter attack of Section 3.3.2.
If disk-space wasting is used, there are the additional limitations that backup service will not be available for 2 weeks after a crash, and if prepayment is used, backup service will not be available for the first 3 weeks and growing backup-storage space will take 3 weeks.