Q: When Netstumbler detects certain ad-hoc clients, they seem to multiply with new BSSIDs, is this a bug in Netstumbler?
A: No, this is normal behavior in IBSS, or ad-hoc mode as defined in the 802.11 standard. An ad-hoc station will scan for an available IBSS to join. If it cannot find one, it will generate a random IBSSID that will be used by subsequent stations joining the network. Some standalone IBSS clients will repeatedly scan and create a new 1-member IBSS, this will appear as a steady stream of new networks with identical SSIDs and different IBSSIDs.
Not all wireless devices exhibit this behavior, but it should be possible to replicate it with Lucent/Agere based devices. Some devices will generate an entirely new key on each scan pass, while others only cycle the two octets in the middle of the IBSSID.