Cloud costs
So if you move all your services to the cloud then $VENDOR can up the price whenever they feel like and you have no choice to pay. If you're running on-prem then you've paid for the hardware and it's not going anywhere, you may have even negotiated support for three or more years on the gear and the OS/hypervisor/whatever to run on it. I wonder how many PHBs will rethink the blind move to the Cloud that many organisations seem to be going for.
Biting the hand that feeds IT
