Quick plug for a worthwhile petition here:
It's been set up by Bruce Forsyth to get vets to scan all dogs as a matter of course, for microchips. As the scheme stands at the moment it's not a lot of use unless you just lose your dog! If it's stolen, the microchip is never likely to be scanned so it doesn't help! - This petition aims to help the situation. There is also a downloadable car sticker!