I think "if the system as a whole doesn't require ACID, maybe the pieces don't" is correct and useful, but it still requires looking at the pieces and seeing if that's the case. In this case, I think that the system is relying on the ACIDity of some components to ensure Eventual consistency - it's conceivable that an alternate method might not, but one would have to be proposed and evaluated.
I think this is reasonable; but then the problem becomes that while consistency may be eventual there are nevertheless fixed deadlines to meet. Soft realtime consistency isn't good enough when the annual report has to be printed.
Personally, I feel that ACID is an abstraction achievable only within single, non-distributed systems. Not a very compelling insight, I hear you say.
Well no, but ACID is a tremendously advantageous state of affairs and I feel it should be surrendered only begrudgingly. I think it is better to repair it than to abandon it wholesale at the first sign of mild inconvenience.
Even though it is, in a physical sense, untrue, it is a useful untruth. Newtonian physics is wrong. It's also what we use to build bridges.
