[Zope3-Users] Use Case for a Tree of Adapter Registries?

[Jeff Rush]

I've read the code for adapter registries, how there is a global one and any 
number of local ones, arranged in a tree and that each can be disabled.

But I can't figure out when you'd want to make use of such an arrangement. 
The docstrings and .txt files use abstract examples, for unit testing, and 
don't provide a motivation for this feature.

Related to that, the global registry is loaded at server startup time from the 
various .zcml directives, and I presume that the only way to loaded up a local 
registry is thru-the-web, right?  Which means all local registries are 
persistent in the ZODB, I think.

Can anyone nudge me onto the right path?

-Jeff