[10000truths]

The problem with this is that you have to be really damned careful how you split things up. If your separate data stores end up having to be joined together later on because some new business feature requires them to be cross-referenced, you're painted into one of two corners:

1. Merge the two services (and their data stores) into one and cause havoc downstream of either service

2. Burn through your network latency/throughput budget trying to reinvent a DB join across RPC boundaries (and god forbid if you can't batch multiple lookups in a single API call!)

[dahwolf]

Exactly. Software developers will never learn that the separation of concerns is a myth. In reality, UI, business logic and data are deeply entangled. Hence, moving these things apart makes everything worse.