Is there a way to avoid exposing a version number over a wireless AP?
I’ve tried to put an empty string into “Radio Name” but that did not change anything. The scanner still shows the version number and the flags APRB (A - Active, P - privacy, R - routeros network, B - bridge) for the AP.

The scanner uses several techniques to query the radio, like “ip neighbor”, “snmp”, “SMB” etc.
You need to disable or firewall them all where relevant.
edit: well, that was about the IP scanner. the radio scan may see even more.
This information along with the radio name and model number is directly encoded into the 802.11 beacons - you can not remove it (yet).
http://forum.mikrotik.com/t/removing-mikrotik-elements-from-beacons/118497/1
Thanks. I hope Mikrotik will add an option to hide this sensitive information.