By multitasking, one takes down the otherwise normal degree of alertness and spatial awareness that comes about from being focused on the singular task at hand. One does not need to then strike out against the presumed stalker. The question is one of intention. If one is not alert and is caught by a person sneaking, it is the lack of alertness that is to blame, as the onus of external stimulus is not on the person who is minding their own business, but rather on the person receiving the auditory and visual feedback.

As has been pointed out, in a real life, physical situation, intention is crucial in assigning a would-be assailant's motives. So long as a person is not in a location that he is legally forbidden to enter (i.e. trespassing), then he is free to go and come as he pleases. There is no legally recognized 3-foot-personal space, it is merely a social convention which may be compromised without recourse.

Oh but if there were! I would totally press charges on the person whose field of vision I incidentally passed through. The right to be free from glances is paramount!

But seriously, on a forum, you can post, or not post; visit, or not visit; abide by the dictates of the site or risk banishment. It's really as simple as that. If you feel violated by it, then clearly it is not something to continue to pursue.