Will the Synagogue Ever Go Virtual? discusses the matter and points out that the halacha requires physical presence. Even in two rooms in the same house, separated by a wall would prevent the two groups from being part of the same minyan.
Can those ten people be gathered via webcam?
Apparently not. Jewish Law specifies that the constitution of a minyan
is when “all ten are in one place.”2 Even if they are geographically
close but separated by a wall, the ten people cannot be considered a
Shulchan Aruch Harav, Orach Chayim 55:15
An interesting way of considering this
From another perspective, in the infancy of the World Wide Web, Rabbi
Kazen was asked about virtual prayer. He responded:
Can I have a virtual meal? How long is it going to hold me for? I can
read a recipe, but I still have to go out there and buy the eggs, buy
Yes, the prayer itself can be read off the Net. But the actual act
needs to be done by a physical person. The concept of Judaism in
general is using the material - the animal cowhide, the hair of the
lamb created into wool - so that there's actual participation in all
the different four levels: the inanimate, the flora, the fauna, and
the human being - all into one aspect.
The quorum of ten people requires ten physical bodies [in the same
room]. Each individual person has a spark of G‑dliness within them,
which is the soul. We don't necessarily see the spiritual reality of
what is happening at the time, but certain things have to be done with
physical people, just as food has to be eaten by physical people.
The Soul of Cyberspace
One could note that the Conservative movement attempted to come up with a way of allowing this but could not do so in a paper written March 13, 2001. Their final conclusion was that a virtual minyan was not valid.