There's already a concept of setting flags to avoid traversal of certain filesystems, and given the proliferation of virtual and networked filesystems, this seems useful: /proc, /sys, /dev, /udev, and a few others (it's getting to the point I don't recognise a full mounts listing readily anymore under Linux).
With the concepts I'm considering, in particular, of the tree as being essentially search traversal rather than a static filesystem (not even one with lots of symlinks all over the place), the potential to create some deep dives or recursive tangles is pretty high.
Another example: tools such as 'locate' or Spotlight shouldn't attempt to traverse this tree when generating indices. Instead, they should query it when requests are made.
Information and metadata leakage is another key consideration when moving data off local host and/or caching among hosts.