After a lengthy business trip that took me through 6 countries in Africa and Europe I was questioned at YYZ about where I had visited. No problem.
Then he got into why I was out of the country, what I was doing there and who I met with. I drew the line right there and explained I was a returning Canadian citizen, a resident, wasn't going to answer any more of his questions and to send me to secondary.
He scowled, scribbled on my landing card and off I went fully expecting to spend the next several hours there. I was waved through the next stops, gathered up my bags and went home.