Pretty neat if you think about the technology as a smarter cache. One could easily see certain applications, such as blog networks or Twitter alternatives.

Security is easy in some cases. Sign your log appends. Security around transactions without a central authority is pretty complex. Whats the solution there? Block-chain type things? It would have to be application specific I suppose.

I never gave FirebaseDB a shot because it felt like too much vendor lock in but this might be interesting to try one day.