http://thinkdistributed.io/blog/2013/08/28/causality.html
This website is hosting some very interesting conversations regarding distributed systems and topics on concurrency.  The above link is to a conversation about Causality. The root of the conversation deals with how systems can maintain the consistency of a state of a database or a document.  Warning: The conversation is very scholarly, but it does a really nice job at describing the current best theories on concurrent data systems.

I use BigCouch at the company I work for, 2600hz.com where we build Kazoo, a distributed communications platform for Voice / Video / Text etc.

I will no doubt be continuing to watch these conversations over at thinkdistributed.io