First of all, it's rarely used. At the end of the day, it's a safety valve for those who are in extreme conditions and could not establish properly their identification or their qualifications as electors. Secondly, it's done very publicly and openly in front of officials, who take detailed records of the proceedings there so they can be checked afterwards if need be. It's also done in the presence of observers from candidates, who can challenge and certainly bring matters to the attention of Elections Canada if they have concerns about the legitimacy of the procedure that has taken place.
Again, I'm not sure that the risks there, which to me are minimal—truly minimal—warrant denying a legitimate elector to cast a ballot. That's another charter issue.