These are always fun exercises. There has not been so far any way to know for sure. We can make a reasoned guesstimate, and I know this has been done on FT in the past. Including some who flame. Whatever. United forum did a MM roll-call thread in 2007 and came up with 300+ MM after 5 years of the thread (!) to 2012. It looks now like closer to double that in the posts since. I did not count. Based on this thread there are about 600+ 1MM. About 80 2MM and 20+3MM. Including one poor chap at 17MM. That is in a country with three major international carriers.

Assumptions:
1. A minority of these people would be on FT.
2. Those that are on don't always post. I am super guilty of this.
3. The AC and UA ratios are even remotely similar, given Canada's lower population but longer travel distances and only one major international carrier.
4. Other threads here have estimated / had apparent information from Andrew Yiu that there are about 10,000 SE's and 35,000 people with status below SE annually.
5. Based on my frequent AC travel and bag tag gazing. Full disclosure : I am a newly minted AC2MM.
Based on this I will put forth the following:
1MM ~ 1250
2MM ~ 150
3MM ~ 20

Consider pot re-stirred.

diddy