the throttle.module is only interesting and usable by high-traffic sites like kerneltrap.org and/or drupal.org-a-like sites. IMO it's too much for core, because there are lot's of people who use drupal for their own personal site and small business sites. the throttle.module is a little bit of an overkill for sites like that.
The throttle is useful to sites that have limited resources and usually are not that busy. It is actually less useful to consistently high-traffic sites, as by necessity they will already have the required infrastructure to survive high loads.
The throttle works well for a website that's on a shared host with limited CPU and bandwidth, that usually only gets a handful of visitors, and then is suddenly Slashdotted. Of course, it will only help in that case if it has been enabled and properly configured.
This is exactly the kind of information that would be useful to people. A description of what the module does, who it is for and an endorsement of it's quality. I wonder if we could start a book about this somewhere.
Cheers, -Jeremy