Who knows what it really 'means'. (And meaning, at least as represented by posters here, seems to vary a fair bit based on oxen ownership.)

It seems to indicate that both concepts are more fluid than feels comfortable. To some extent, it feels related to bandwidth/latency/maybe the direct linkage and chemical interaction between brains - as that increases, the boundaries become blurrier.

Peter Watts had great fun with this idea in Echopraxia (http://www.rifters.com/ ).