I think any responsible network admin faced with this challenge would have to start thinking about delivering services to these devices on separate, very carefully planned networks, since any network accessible enough for ad hoc devices would need to monitored very closely for abuse, malware infection, and various other things too... You might even have to go to the point where you establish a NAC policy for this network and allow the NAC system to ban devices based on their behavior. If it's just putting out normal amounts of traffic, checking email, surfing the web, no problem. If it's systemically scanning devices in the data-center, that's a problem, and I'd rather that device be automagically banned than find out later a drive-by attacker with an iPad sat in the parking-lot and reconned my network.