Dr. Fellegi spoke quite eloquently on this at the International Statistical Institute. He said that any survey in which you compel responses is inherently privacy-intrusive. The question—and it's a question parliamentarians to some extent have to answer—is whether the benefit is worth the intrusion. That decision, in the case of the census, lay with the Governor in Council, and they took that decision.
On March 8th, 2011. See this statement in context.