Names are not cheap
A recent sysadmin discussion here wound up with one of the participants suggesting that we deal with a particular issue by creating a new hostname, because after all names are cheap. This remark crystallized something for me.
I disagree. Names are not cheap, they are actually expensive. Names look cheap because they are easy to create, but they create clutter and uncertainty (over what name is still being used by what) that makes them expensive in the long run.
(Once you have enough names and enough uncertainty, you become overwhelmed; cleaning anything up requires an extraordinary amount of work, so you just pile more names on top without even bothering to try to figure out if you really need them. Maybe you could reuse an existing name, and maybe not; it is simpler and faster just to assume you can't.)
This holds for all sorts of names, not just hostnames. I've also seen it in at least Ethernet addresses in DHCP registrations and in Unix logins that aren't assigned to specific identifiable people (whether they are for bits of software, collaborative projects, or generic visitor accounts).
(The bad effects of clutter aren't restricted to just names, of course. Many things can become so cluttered up that they're all but impossible to understand, so the only way to proceed is to try to build your own addition on the side.)