This discussion comes up equally in the homesteading and big farm areas equally.
Everybody hates the censues, finds thrm a waste of time, and fills them out very fast with numbers out of their head in 2 minutes or throws thrm away.
Tiny homestead or big 10,000 acre farm, all the same.
The data collected makes a nice 'census of agriculture' book, now online:
http://www.agcensus.usda.gov/Publications/2012/
This data gets used by lobbiests and congress people and state and county govt people to work up govt programs, extension programs, and so on to 'help' people in this country and other countries.
If you have 500 CSA garden farmers filling out the forms in your area, you will find in 5 years a lot more services available to educate people on small gardens, help for setting up farmers markets, space for farmers markets, fliers on govt buildings promoting small farms, etc.
If the 500 people around you fill out 1000 acre corn and soybean forms, then you will see a lot of that info show up around you instead.
Both you and the big farmer will shear at those things, and find it a big waste of tax money, and occasionally you'll actually, maybe indirectly, use some of that material or assistance or space.
Anyhow, those census' are a lot of angst over nothing. Nobody really cares. The govt is persistent about getting info from you, they will mail, call, and even visit you. They won't throw you in jail. They will pool your info in a big fat book as I linked, and that's the end of it. If you send in very accurate and detailed info, you might be the only one......
Don't worry about it too much. I think I've got 2 on my counter here and just erased the message left in my answering machine. If they catch me on the phone, I'll answer the questions as fast as I can, more or less close to what I recall my crops are. I will be faster than I am accurate.....
Paul