Like they say, Cluin, if you've got nothing to hide, you've got nothing to worry about.
As for this being useless.... There are a lot of pretty nasty people out there whose ID particulars are already known, but they're somewhere in the world beyond the reach of U.S. security. If it stops them from coming in or catches a few of them trying to, it seems like a pretty good idea to me. The cost? About $1.50 per person per year. Seems like a bargain....