[tor-talk] Why so may exit node IP addresses in the TBB?

[Allen]

>>> It used to be that, if you opened five sites in TBB, all five would use
>>> the same exit node. Now it appears that each of the five sites has
>>> the IP address of a different exit node.

It started on the alpha development of 4.5[1]:
>
> "This release features [...] isolation for circuit use. All content
> elements for a website will use a single circuit, and different websites
> should use different circuits, even when viewed at the same time."
>
> [1]: https://blog.torproject.org/blog/tor-browser-45-alpha-1-released


That doesn't answer the question though why the different circuits use
different exit nodes.  They could all use the same exit node.  I recall
seeing fair bit of debate over how many exit nodes a Tor client should use
and how often it should switch exit nodes...