Spotted this article on CNN about police officers using wireless handhelds to look up your personal information. But a more disturbing tidbit was buried deeper in the article, which was that according to a recent Supreme Court decision, you can be arrested for refusing to give your name to the police. In other words, failing to identify yourself is now a crime.
Not only is this a little scary in itself, but if you logically extend it, it presents some nasty precedents. What if you're required to carry an RFID tag with you (buried in your driver's license, for example)?
Reading through the second article, it says that the above ruling does not actually require you to identify yourself unless reasonable suspicion exists (roughly the same burden of evidence as required to pull you over). The RFID question remains, however, since the problem with RFIDs is not only that it's easily automated, but that it can be done without your knowledge (unlike an ID check).