I have been secondaried at Canadian customs many times. It was often annoying - they once decided to have a look at the files on my USB drives because I had old players cards attached to them (easy to misplace a tiny flash drive otherwise...) and that was "suspicious". Asides from annoyance, no real problem.

Then again, before my first trip to Canada I had seen most of Border Security (Canada) - definitely worth viewing. If only to hear one of the genius agents declare "Well, he had 9,000 dollars on him - that's definitely suspicious - why not 6,000 ? Why not 13,000 ?.....