Casey Bisson gave a great talk today at ContainerCon and he use the term "pet" a few times (refering to servers), which reminded me of this recent article:

As soon as somebody logs in to a server and starts issuing commands to change the state of that server, its integrity has been compromised. You have no reliable way to get a server in to that state again and your ability to trust pre-production/production parity has now been removed. You've created a snowflake.

Cattle by Kelly Sikkema