Whither and Why the UC Desktop Client Wars?

I was chatting recently with a product manager for one of the larger UC vendors and he mentioned that one of his dev teams is working on trying to integrate their backend server with a competitor's desktop client (in effect, allowing their own desktop client to talk to their competitor's desktop client). I was astonished by this as it is so yesterday in thinking about how people collaborate now.

Skype, Live Messenger, and the Looking Glass

UC vendors by necessity will update their products over time. Usually the journey is straightforward, as in adding new features and functionality or enhancing performance or security. Occasionally the changes are not straightforward and consumers, enterprises, partners, and competitors are left scratching their heads over what the vendor is trying to accomplish. Vendors argue that these puzzling changes they make reflect business or technical decisions that they expect to pay off in the long-run at some measured short-term disadvantage or loss of momentum.