This is against so many IT security best practices, you're probably breaking a regulation if you're in an industry not dealing with selling jewelry on Etsy.
While you're right, BYOD has been an on-going headache in IT for several years now. It's one thing to say unapproved devices are completely not allowed, but reality is when the CEO brings in their shiny new iPad and demands it get on the office wifi, the iPad gets onto the network (however heavily segmented and firewalled).
BYOD for mobile isn't entirely new, but most people doing that have MDM software that MITM's secure connections (potentially) and keeps all office-related software in a sandbox.
Attaching a desktop to an office network rarely has those same mechanisms.
