“Typically we just have the one beta, but we will have some release-candidate builds,” he said. “We’re making nightly ISO updates right now, and people are taking a close look at the release candidate.”
This quotation is obviously taken somewhat out of context and I expect reads pretty confusingly if you don't know the Fedora release process. I suspect the question was something like 'how many pre-releases are there before Fedora 16 comes out' or something, and there may have been reference to Ubuntu's seventy-three zillions beta builds.
So, for the record, it works like this:
For each Fedora release there are only three widely-distributed sets of images: two pre-releases and the final release. Alpha, Beta and Final. I tend to call these 'phases'.
For *each phase*, there are Test Composes (TCs) and Release Candidates (RCs). A Test Compose is built before freeze and hence cannot possibly go out as the release; they're sort of test runs which we use to identify major issues ahead of the freeze point. An RC is built after freeze and should have all then-known release blocker bugs addressed and hence is truly a Release Candidate - if we don't find any further problems in it, it gets blessed and goes out as the release. If things go very well there may be only one RC for a given phase, but usually there are at least two or three. So typically we'd have, for example, Alpha TC1, Alpha TC2, Alpha RC1, Alpha RC2, Alpha RC3, then RC3 would be found to pass all the necessary tests and would be declared to be the Alpha release, mirrored, and announced as such.
Nightly builds happen every day (unless the compose simply fails for one reason or another) and are a separate process; they're just built automatically and left sitting on a server where you can download and test them if it seems useful for one reason or another.
So yeah, there are relatively few widely-distributed and publicized pre-release builds for each Fedora release, but there are actually a lot of composes that get announced and tested on a somewhat smaller scale leading up to those release points. The TCs and RCs aren't really restricted in distribution - if you sign up to the mailing lists or follow the forums, you'll find the links - but we don't go out of our way to announce them publicly and they aren't mirrored across the whole Fedora distribution network, they're just built and put up on a couple of servers. They exist to help us ensure the 'official' pre-releases and release meet the required standards.