The information provided by the Better Business Bureau (BBB) (Better Business Bureau website) while technically correct was not totally accurate when it came to the Census employees canvassing door to door. I contacted the US CensusBureau who stated that the Census Dept is not sending anyone out door to door until the period May 1, 2010 to July 10, 2010. If anyone approaches your door before May 1st, stating that they are representing the US Census Dept., my suggestion would be that you DONOT open your door but politely excuse yourself (by telling them astory like you are getting dressed and could they come back in about10 minutes and immediately report them to the police) hopefully, theywill still be in the area when the police arrive.
After May 1st, if you question the legitimacy of someone identifying themselves as a census worker and they present a Census ID (how many people actually know what a legitimate Census ID looks like???) you can ask them to show you another ID to make sure the names match up on each. All workers will have a census Dept ID and since most people will not know what a legit census badge looks like it may be prudent to ask for the 2nd ID.
The 3rd check is that the census worker at their door should have a telephone number with them to provide to the homeowner to verify that they actually work for the census. The verification numbers are based on where you live so they would be too numerous to place here but for those numbers and general census information call 1-866-872-6868.
[Thanks to Kevin for the info.--former Federal Law Enforcement Officer]