CAR 2
(7A)An aircraft that carries persons on a flight, otherwise than in accordance with a fixed schedule between terminals, is employed in a private operation if: (a) public notice of the flight has not been given by any form of public advertisement or announcement; and
This is the part of the CARs that deals with what you are talking about.
I don't have facebook (I think the whole thing is stupid and I'm gen Y believe it or not) so someone may correct me on this, but as far as I am aware you can either have a public or private setting. If it's set to public then the bolded passage is clearly violated and you can't do it.
However, if your profile is set to private and only your friends can see it then functionally it's the same as calling them all indivdually and telling them (which is legal) but more efficient.
Still expect CARA to hang you out to dry if you are caught on some stupid interpretation by a crusty old FOI who woke up on the wrong side of bed.