Today I realized that my ideal home directory system (network mounted homedir, but with offline access) is in fact, impossible to implement. Provably so, thanks to the CAP theorem aka Brewer's theorem.
So: I have to choose to lose one of: Consistency, Availability, or Partition-tolerance. Let's review the options:
Conclusion: the best of all worlds is impossible. If you can guarantee network stability, then by all means, give up partition-tolerance, and use a pure network filesystem with a single authoritative copy of the data. If you expect network outages, or need access to the data before network is up, give up consistency, and use something like Dropbox that keeps a local cache and syncs that with the remote "authoritative" copy.
It's interesting to note that the best possible solutions to this problem already exist (and see wide deployment). Thus, I claim that network-based storage and synchronization is, for all intents and purposes, a solved problem.