The leading case on this is Feist, a telephone book case. http://www.law.cornell.edu/copyright/cases/499_US_340.htm As an interesting note, the phone company had been introducing fake listings: "Four of these were fictitious listings that Rural had inserted into its directory to detect copying." For copyright, originality is a constitutional requirement and copyright cannot attach to a bare compilation of known facts. However, "if the compilation author clothes facts with an original collocation of words, he or she may be able to claim a copyright in this written expression."

The court held that "the names, towns, and telephone numbers copied by Feist were not original to Rural and therefore were not protected by the copyright in Rural's combined white and yellow pages directory. As a constitutional matter, copyright protects only those constituent elements of a work that possess more than a de minimis quantum of creativity."

Yeah, I would tend to agree with this. These data are derived from work originally done by the U.S. federal government. If they had chosen to make it freely available without a FOIA, public domain would have applied. I don't think having it being a result of a FOIA changes anything.