More I think about RFID, more doors open up.  While thinking about the privacy issues rising from associating RFID with a person via purchase records, I thought of a couple of unique ways RFID might be used.

One idea is to record RFID tags on people and things moving in and out of an area through gates.  An alarm is raised when an unknown RFID is detected within the area.  Software is simple, just a database of RFID tags with optional good-til timestamp so Pizza can be delivered within the area.

Another idea is to use a set of RFID for authentication like "Please Wear Yesterday's Underwear to Authenticate".  Seems silly at first, but requiring a minimum number of RFID known to be owned by a person or asking for a specific RFID to authenticate is not entirely useless.

Update #1:

Alient Technology RFID tags can be read 15 feet away.  That's enough to cause concerns.  In fact, I think RFID tags with wider range than average 'personal space' is of concern.  RFID tags with smaller range usually requires violation of personal space like waving a hand-held metal detector around your person.  Of course, hidden readers like 'shoe-readers' embedded in a line of bricks along a walking path is a problem.

Perhaps some legislation is necessary to require readers to be clearly marked and readers for RFID tags with wide range be licensed to be usable within specific areas.   Requiring RFID readers to have embedded long range RFID tags is can help so one can walk with a RFID detector and not worry about RFID readers.  Same can be used to make sure long range RFID readers stay where they are licensed to operate.

Another thought is that 'Opt-Out' RFID tags might be a good compromise.  I could wear one as a necklace and it could tell RFID readers to ignore any RFID tags I might have on.  Again legislation is necessary so this behavior can be built-into RFID readers.