I'm a pen tester for a mid-ish sized company. I recently got approval to remove "port security" (802.11x) on a single port within the building. It is amazing the amount of access I now have (using a non-company managed laptop, plugged into this port).

Once a bad guy has equivalent access, they are very deep into our network (and have bypassed multiple layers of controls).

I don't think my company is unique in any way. I would expect this level of access at most companies to be game-over / large problem.