I know a family who is homeless. Will they be counted? Probably not because they do not have an address to receive the form.
'At the Census Bureau we understand that these can be challenging times for many people. Because of this, we created the Service Based Enumeration (SBE) operation. The SBE is designed to provide an opportunity for people experiencing some form of displacement or lack of permanent address to be included in the census, by counting them at service-based locations, such as homeless shelters, soup kitchens, etc. The Be Counted form is another way people can take part in the census. Be Counted forms are census forms that are available at various community locations for use by people who either did not receive a census form in the mail or who believe they were not otherwise included on any other census form.'
http://2010.census.gov/2010census/how/questions.php
And the penalty for lying:
'What if I provide false information?
According to Title 13, Chapter 7, Subtitle 2, anyone who willfully gives an answer that is false could be fined up to $500.'
Title 13
Sec. 221. Refusal or neglect to answer questions; false answers
(a) Whoever, being over eighteen years of age refuses or willfully neglects, when requested by the Secretary, or by any other authorized officer or employee of the Department of Commerce or bureau or agency thereof acting under the instructions of the Secretary or authorized officer, to answer, to the best of his knowledge, any of the questions on any schedule submitted to him in connection with any census or survey provided for by subchapters I, II, IV, and V of chapter 5 of this title, applying to himself or to the family to which he belongs or is related, or to the farm or farms of which he or his family is the occupant, shall be fined not more than $100.
(b) Whoever, when answering questions described in subsection (a) of this section, and under the conditions or circumstances described in such subsection, willfully gives any answer that is false, shall be fined not more than $500. (c) Notwithstanding any other provision of this title, no person shall be compelled to disclose information relative to his religious beliefs or to membership in a religious body.