An undesirable characteristic
This may be an extension of guarding behaviour or it may be a separate factor.
Similarly, it is often associated with head butting behaviour, but I am unsure of any direct linkage.
Basically... after colony disturbance a number of bees will pursue the beekeeper or helper at about head height and for a variable distance that may extend to hundreds of metres. This may be accompanied by "dive bombing" or "head butting" or maybe just keeping station with the receding person. Sometimes the person being followed will report that the bees appeared to be "staring them in the face".
I mark fairly heavily against this activity on the record sheet and will re queen such colonies at the earliest opportunity. The behaviour is compounded if the followed person is intimidated by the process (I presume "fear pheromone" is at work here)
I have a personal feeling that the head height and following aspects are related to carbon dioxide in exhaled breath (or halitosis), but I have no evidence for my conviction.
I have very rarely experienced "following" and I can only assume that is because I heavily cull any colonies with undesirable characteristics. R.P.