Last summer, Bachmann declared that she would not completely fill out her Census form, that she would only give the number of people in her home and not provide any personal information beyond that. This is in fact illegal, and could have resulted in her family not being counted. Bachmann said she was doing this in order to prevent her personal information getting into the hands of the government or ACORN.
Bachmann also warned that Census data could be used for nefarious purposes, linking it to the Japanese-American internment during World War II. Bachmann also questioned the kind of data that the government collects in both the Census and the longer American Community Survey, which is conducted on a monthly basis by the Census Bureau in order to maintain the government's demographic data. Among other things, Bachmann objected to questions about people's mental health.
At about that time, a group of Republican congressmen released a letter criticizing any attempts to boycott the Census, calling it "illogical, illegal and not in the best interest of our country." The letter did not directly name Bachmann, but it's topicality was pretty obvious.
In January, the Minneapolis Star-Tribune published an editorial calling upon the state's citizens to actively participate in the Census, due to the fact that Minnesota is in a close competition with other states that could result in it losing a House seat. The paper noticed that Bachmann had long since stopped criticizing the Census -- and that the most logical outcome of such an event would be that her own district would be cut up and spread among its neighbors, given the nature of the boundaries.