Fedora Users — yum.conf clean-up

When I first installed fedora core, I was entirely clueless about yum, although I knew about apt from the debian experience I have. Anyway I didn't see that great page that says, basically, rpm.livna.org will provide most of the things that aren't provided by fedora.us, and that the combination of the two will mostly do everything.

So before I figured that out, I needed to install k3b, wine, libmad, and as a result I have a bunch of other repositories listed in my yum.conf. Freshrpms (libmad and other k3b dependencies), xcyb.org (k3b), sunsite.dk (wine), for example. I was about to add Dag Wieers' repository to get Java, when I decided I needed to clean up yum.conf.

What happens if I remove them now, and no other repository updates one of the packages I have installed? Do I get some warning that I have "orphaned" packages? Or do I just have to figure out myself which packages are no longer being updated? (Or try to figure out ahead of time, which source provides which packages).

The reason I ask is, yum will go faster if I have only the minimum number of repositories set up. So I want that file to be as short as possible. Also, obviously, I don't want to use bandwidth at any more repositories than is necessary.

Thanks,
Matt