Great article from Zeus Kerravala. Comments later.

No Jitter | Presence, not VoIP is the Foundation of Unified Communications

"Unified communications (UC) has been a hot topic in the vendor community for the past couple of years, particularly with the traditional communications vendors. The majority of positioning that I have seen around UC positions VoIP as the foundation and then UC being the “stuff” that gets built on top of VoIP. I do believe this was conventional thinking for quite some time but this “old school” thinking needs to stop or UC will take years to reach its potential. Also, it’s just flat out wrong. Presence, not VoIP, should be thought of as the foundation for UC."