Sounds like we need a simple and easily memorable response to the "unaccountable" argument, then. Magnatom made a good comparison with pedestrians, which I liked, but Mr Moton claimed (incorrectly) that wasn't relevant as pedestrians don't use the roads.
I'd be thinking something along the lines of "this is a valid concern and obviously nobody is suggesting that cyclists should be above the law. But in practice, if you drive regularly I'm sure you see many many laws broken by all kinds of road users which the police just don't have the time or the will to tackle even if they're told the full number plate and a description of the vehicle - because, rightly, they will be concentrating on the more dangerous behaviours. So I think the question that needs asking about registration plates for cyclists is how often the cyclists are actually causing danger to other road users, and is the problem big enough to be worth introducing such a vast bureaucracy in registering them and enforcing that? And on that note it's worth looking at the hire bike scheme in London which does have licence numbers on the bikes, where we see that over the x months of its operation there have been a total of only two offences which were reported with the bike registration numbers"
I wouldn't go down the "it would discourage cycling" route, because the listening motorist is not automatically going to accept that encouraging cycling is a good thing and convincing them of that is a whole other argument. And it's too long already.
That's a fantastic argument. Although I would add the discouraging cycling thing as I think most motorists understand the benefits.
; for some reason Moviemaker never like the MP3 (I've just converted it to a .wav and it likes that 
