Today I struggled a lot with a stupid bug, because I was using the RegisterListenersPass, and I was passing the wrong service name for the EventDispatcher. If the container complainer with a ServiceNotFoundException I would have catched that issue days ago! There's a reason behind this? Could we make this change?

// Symfony\Component\EventDispatcher\DependencyInjection\RegisterListenersPass

    public function process(ContainerBuilder $container)
    {
        if (!$container->hasDefinition($this->dispatcherService) && !$container->hasAlias($this->dispatcherService)) {
-            return;
+           throw new ServiceNotFoundException($this->dispatcherService);
    }

Obviously we can think of a more convoluted solution, but still this issue remains, IMHO. And 4.x is coming, so a BC wouldn't be an issue here.