The Census and the Constitution

Last summer in 2009. I had census people with the right credentials show up in my neighborhood three different times to find out how many livable dwellings there was. I think coming through the neighborhood once would have been enough. I just received a notice in the mail that I will be sent a census form. I figured just sending the census form would have been notice enough. Doesn't take a rocket scientist to figure out why its costing so much to do the census.