My boss at the mouse facility where I used to work was looking into developing reusable chips for the mice - we already used a scanning system they have/are developing (it's amazing, even tho I left the place I would use that program for all my animals if it was available to the public), however, instead of RFID chips we had to use ear tags (not plastic tags, but punches out of the ears) to identify each animal. If a chip could be made for something the size of a mouse, he would have implemented it regardless of cost, I just think we are still at a lower level of technology, but it will come in time.
I would have my animals chipped for peace of mind more than anything else, tho if readers were available for the owner, imagine the level of book keeping - and how much easier sending in our record books would be. Hmm, anyone want to write up a proposal to DECC?