My ceremony was this past Monday. Around 120 people took the oath, which is one of the largest groups I've seen in Edmonton.
I had a really busy day and really wanted to be done with it as fast as possible so as I was checking in I asked the guy if I had to stay for the singing of the national anthem. I was in the first row (chair #2), and had already wasted an hour of my day waiting in line. He got this stern look on his face and told me that I had to, or else I won't become a citizen. I had seen, on a previous occasion, someone being chased down after getting their citizenship certificate and told that they have to stay for the anthem.
So I asked him if he could tell me what legal authority requires sticking around for the anthem. I had reviewed all the legislation and the regulations, and they say nothing of the kind: you take the oath, you are a citizen. That really set him off, so he turns to one of the more senior officers there and says "this guy doesn't want to take the oath". I said, excuse me, I never said anything of the sort. So the senior officer says, yes, you are right, but we'd like you to wait as a courtesy for everyone else behind you.
So I said fine, especially since I was sitting 5 feet away from the CJ's podium... if I had been a couple of rows back, I would have just got the hell out after getting my certificate.
Luckily, they asked that people not take photos with the CJ until after the ceremony because of the large number of people taking the oath, so it didn't take all that long.
I wish I had thought of it at the time, and said: "Courtesy? You mean a courtesy to all those people behind me who applied two years after I did, but are becoming citizens on the same day as me? You mean it's not fair to make them wait an extra 30 minutes?" ;D