I used to be a regular many years back, but I was a bit of an eco-warrior type then (though I did have a driving licence I couldn't afford a car, my time was spent sabotaging hunts and campaigning against the Criminal Justice Act.
It was a bit anti-car rather than pro-bike, though the Pedal Pushers group added some balance and stopped it from being purely "dreadlocks on parade"
I've never bothered to partake in any more since I've rediscovered cycling in the last year or so...I would if is was CLEARLY targetted at one particlar notorious blackspot, or making a statement if a cyclist were to be killed and the sentence ridiculously light, but I don't really see what annoying other folk does