In theory, anything is possible. In practice, we are not talking about information that is so personal that people are giving away family secrets. People give much more problematic and sensitive information to banks, insurance companies and so on. That is really sensitive information. The data that currently come out of the census are much less sensitive that the information out there on most people that is controlled by private information banks. In that context, I think that the implications of the questions should not be overstated.
On August 27th, 2010. See this statement in context.