Or sign posts that thieves previously detached from the ground and waited for an unsuspecting cyclist to lock it to the post. Lift sign post, lift bike.

We have a bike post at work like you described, a simple socket wrench or one powered and a 9/16ths would get you a good haul. It's a s shaped contraption with a few more curves. If I ever use it I will probably use the middle of the rack, maybe lock the chain to one side and the u to the other. Currently I keep my bike locked inside the stairwell chained to a permanently attached structure near the stairwell out of the walkway.

I saw security walking over to the stairwell the other day, but no one has said anything yet. But there was a wet floor sign in front of my bike when I went outside for lunch....