Zombies spawning and spreading like a cancer, leaving crying orphans in their wake. Rogues flitting in the background, hirable for a price and always ready to stab you in your back.
These all sound like elements to a cheap, zombie apocalypse film, but spawning, zombies, orphans, and rogues are actually components of VM sprawl.
VM sprawl is frequently defined as the unwarranted proliferation of virtual machines in the virtual environment.
VM sprawl is a common problem to virtual environments that are not tightly controlled by a single person. In years prior, while not uncommon, it was still relatively rare to inventory your server room and find an extra server or two. In these days of easy to deploy virtual machines/servers, it is much easier to add VMs and forget about them.
Unless you employ draconian controls, you will usually face VM sprawl of some severity if you are administering your virtual environment.
Outside of making your environment difficult to manage, unchecked VM sprawl can lead to other, potentially dangerous issues. Unchecked growth can lead to bottleneck situations, where your potential growth is checked by one or two resources. These VMs may have inappropriate privileges to the network, such as an unsecured domain controller or directory server. They could be a potential virus vector for the rest of your computers. They could be used by unscrupulous hackers to access sensitive information on your network. You could even face legal problems if hackers did access sensitive information, especially if you are subject to government or industry regulation.
In short, VM sprawl and overall VMware performance monitoring can become a huge problem and risk to your organization.