Possible to have too many partitions?

Situation:

I test the Mac version of software for a certain company.

This is a relatively new job, and I was given access to an iMac and a Macbook Pro.

The software I test is supported in various versions of OSX: 10.7 through 10.9 and soon, Yosemite.

My IT guys don't want me partitioning the HD of the iMac into 4 partitions...I wanted to install each version of OSX our software can be run on. They would rather I do a VM.

Question:
While I don't mind using a VM, I still want to know if there is any other reason (besides convenience) that I shouldn't create 4 bootable partitions? Initially the IT guy told me he didn't want more than 2 partitions on either of my machines. Why not?

The main reason partitioning doesn't sound so bad to me is, I am restarting my computers all the time with installing/uninstalling software. Sometimes VMs are slow and do weird things...I would honestly rather just partition.

Thoughts?