For the stats-junkies out there, here are a few interesting visual representations of who is federating, and how they're doing it.
(Hover over graph segments for quantities)

Deployed Versions

Proportion of registered organisations running each version of UC product

14 402 154 751

Cloud vs On-Premises

Proportion of on-premises deployments against hosted/cloud solutions

111 923 290

Federation Security

Split of registered organisations offering open vs. closed federation

1381 396

World Domination!

Just look at that global coverage!