So here's what I have for Firebase pros and cons so far:

Pros:

• Autoscaling built-in
• Can start for free (only need to start paying once we hit 50 connections)
• Robust APIs for Javascript (including several frameworks like Angular), iOS, and Android
• Built-in support for authentication services like Facebook, Google, and Twitter
• Declarative Security Rules model allows us to enforce read/write privileges and data validation throughout the tree

Cons:

• Need to build indexes manually
• May need to build "event log" manually as well (in separate sub-tree?)
• Implementation of REST API could be difficult on embedded platforms
• Data validation rules do not support complex objects directly (you'd need to validate individual child nodes separately)

Other Concerns/Questions:

• Vendor lock-in - if we need to get all our data into a different platform, how difficult? (just getting an export may not be good enough)
• Cost-comparison to self-hosting in AWS