Why and why not Fedora
There's a certain perception that Fedora is the beta-quality testbed for Red Hat Enterprise (to condense a comment from an earlier entry), and this is why you shouldn't put it on any machine you care about. This isn't the case, but I think people wind up with this perception because they hear the accurate suggestion that you probably shouldn't put it on servers or production machines unless you really know what you're doing.
Fedora is supposed to be (and by and large is, for all that I sometimes gripe about it) a real, release quality Linux distribution. Fedora is unsuitable for 'business' or 'production' use for two reasons: versions aren't supported long enough, and it is willing to include relatively bleeding edge software versions.
The support period is the real killer, as each Fedora release is only supported for about a year (the standard support period is 'two releases plus a month', and Fedora does a release roughly every six months). For many organizations, us included, an update a year is both too much work and too destabilizing; we want to run servers and desktops without significant changes for much longer than that, and in some cases our users demand it.
(Also, a month is simply not enough for most places to build, validate, and deploy a new OS release, especially since most Fedora releases need time to stabilize to start with.)
That Fedora is willing to include very recent software has two effects. First, things sometime break, don't work as well as desired, or have rough edges, and second, it means that the Fedora environment can change significantly from release to release. To put it one way, every Fedora release is a major release; there are no minor releases. And my perception is that Fedora has a bias towards shipping the most recent version of things instead of the 'most known to be stable' version.
(For example, Fedora 11 shipped with a Firefox 3.5 pre-release, now updated to the released version of Firefox 3.5. A more conservative distribution would have shipped with Firefox 3 and waited until the next release cycle before shipping something as new and significant as Firefox 3.5.)
All of this isn't particularly unique to Fedora. Ubuntu does much the same thing (although my perception is that their software versions are usually slightly less recent that Fedora's) for their regular releases.
(All of this ties into my (old) views of Linux distributions.)