Decoupling: Events vs. Dependency Injection

Both have their merits, but personally I prefer the event based system.

There are solutions to the 'silent failure' problem:

1: You could have your event router 'do something' whenever an event is triggered which has no registered subscribers. That way, you will get some feedback at least. However, this feedback is still almost certainly outside of the current scope - you could solve this by registering some global 'unsubscribed event' handler. This solution won't solve the silent-failure problem fully, but it could reduce the number of places it's likely to occur, and at least give some feedback (somehow) when this situation occurs.

2: You could just be more careful during development - ultimately the problem of 'silent failure' only happens because the developer(s) have no idea what's going on inside their system. There is absolutely no reason why the 'saveRequested' event should ever not have at least one handler - and if that is the case, then it's still simply the developer's fault.

All that being said, I don't think DI is too terrible either. Swings and roundabouts!