Edit: this kind of covers it: http://veracity-scm.com/qa/questions/102/why-would-you-desig...
I guess upstream is somehow aware of all downstream repos and can communicate with them outside of push-type operations?
The only other option I really see working is having a designated lock node, so you are centralized only when you need to do locking.
"(their primary product is a visual source safe done right.)"
If I may quibble with this comparison, I would point out that we built Vault because SourceSafe is a deeply flawed product, whereas Git is not a deeply flawed product.
We built Veracity because we think DVCS is the future of our industry and we want to be a part of that. I don't think Git and Mercurial are the end of innovation in version control. I think the third generation of version control is just getting started.
We're not interested in trying to convince people from switching off Git or Mercurial onto Veracity. Why would we? Those people are already happy DVCS users.
But there are still millions of developers who have not yet made the switch from a centralized system to a DVCS. Git and Mercurial will get their share of those new users. We hope Veracity will be a viable option as well.