Is SOA about reusability or agility?

David Chappell talks about SOA and reusability as if they relate to each other. I can somewhat agree , but from my point of view reuse isn't the main benefit of SOA. I would say agility is the main benefit and the foremost design goal for SOA.

Comparing reusability and agility in terms of which one is the easiest to achive, reusability is by far the harder challenge. Impediments to effective reuse are deeply rooted in human nature. Agility on the other hand is not.

While reusability belongs to object orientation, agility is the goal with service orientation and achieved with loose coupling between services in a SOA. David is mentioning service orchestration as the way of reaching loose coupling, but doesn't that relate to process management? I recently posted a few rows about the aspects of loosely coupling when it comes to service management and process management. I would say that agility can come from either, but a distinction between SOA and BPM need to be discussed.

Design approach

Some claims that Service Orientation is bottom-up and Process Orientation is top-down. Since a process is encapsulated by a service, this service is higher up in the design then the encapsulated process. But, this service is on the other hand used by another process which puts that process up higher in the hierarchy. But who knows, there might be a service on top of this process as well. So, with mathematical induction one can prove that none is more top-down than the other.

SOA vs BPM

Are SOA and BPM competing with each other, in aspect of making apps more loosely coupled?

The main idea with SOA is to be in control over the endpoints and the traffic between them, right? Service Management let you reroute the traffic between endpoints depending on content, header, etc. All this Service Management stuff make the parts of a system more loosely coupled to each other and easier to reconstruct on the fly.

BPM has a similar goal of making things more loosely coupled. But the way
Process Management handles loose coupling is by making the execution path more managable. In the same way Service Management can modify the traffic flow on the fly, Process Management can modify the flow of messages between subprocesses or other services. That type of managability is related to the flexibility in the implementation of the service, rather than the coupling between them.