http://en.wikipedia.org/wiki/Vancouver,_Washington

Seems hard to believe it had that many visitors, though.

That was a bug in the list. Toronto had only 7000 visitors to LW last year. However, Vancouver was actually listed twice on purpose because it was in analytics twice. I assumed at the time that one was Vancouver, BC and the other was some other major world city named Vancouver... but now I'm not so sure there is another city named Vancouver that could credibly have had ~5,000 visitors as well. So that bug is by design but I'm not sure what that's all about.

Anyway, Canada is still well represented on LW and Toronto is easily the best city to start Canada's first LW meetup. If you won't start it yourself, you should at least bring this up a bunch and goad someone else into doing it. Similarly sized cities like Pittsburgh, Sunnyvale, and Cambridge have all had meetup before.

It is not at all clear to me why a single half-mirror should result in two multiplications and not an addition in the case of there being more than one photon. After all they are added up when they strike the detector.

It is completely unmentioned why this would be the case, and would seem to bear explanation.