Some time ago I enquired about this term anonymous from the TSX. They replied that a buyer can request that the house number not be reported at the time his/her order goes in. So anonymous can and usually is more than one person. I've been tempted at times to request this but have not done so. Also, I am stuck as to why some do this, except for the obvious secrecy motives. For those who wish to check for themselves, tsx.ca will get you where you can send an email. They replied to me a few days later.