SMILE. Somewhere today you will be captured by a closed-circuit camera at least once, and probably more times than you ever imagined possible, in streets, car parks, shops and even at the office.

The innocent, they always say, have nothing to fear and I have no problem if some poor soul has to watch me pootle round the town centre, if those whose pootling is on the wrong side of legal are also watched.

If, however, you are in the gang which feels the initials CCTV are part of the increasing encroachment on our personal freedom, may I offer you some more initials to consider?

RFID. Radio Frequency IDentification.

On the face of it, RFID seems a good idea. Goods can be tracked as they travel from supplier to store, to the shelf and beyond.

Last year, Asda completed a trial - sponsored by the Home Office, no less - which tracked CDs individually through the supply chain right to the buyer, and carried on tracking if the CD was returned.

The advantages of embedding a microchip the size of a dust mote, linked to an antenna and read by a scanner up to 20ft away, in small, high value items which can be subject to (to use the polite term) "shrinkage" are obvious. It seemed a great use of technology, even if it's still rather pricey for general use.

Then I fell across a scary use: RFID tags in the Cambridge branch of Tesco had been used to trigger a camera which photographed the customers.

It was a trial to monitor stock on the shelf, said Tesco; the camera was a secondary part, linked into the store's existing CCTV.

I'm sure the store had the usual CCTV warning posters; the RFID-ed items were another shoplifters' favourite - razor packs -and the chain said the camera part of the trial was not continued in other stores.

But how will we know in future and in any store? What else could the radio frequency be used to trigger? If this dust-speck of a chip is embedded in the goods, we won't know it's there without being told, and it's also there for the life of the goods.

If RFID becomes cheap enough for general use, that scarf we bought in one store might flag up its presence, and ours, anywhere with a scanner. That's a stride too far into Big Brother territory.

Barcodes came in so that they not only triggered the price at the till but also informed some central computer which monitored stock control. If stock control is all RFID is to be used for on the shelf, there's no need to extend it beyond the transit packaging.

I don't think stores need to know what we look like, where else we go or whether we wear Monsoon or Matalan.