actually i was not talking about speeding, but the fact is bicycle is way too slow to share the same road as car. Not only this is dangerous to the cyclist, the cars also need to slow down unneccessarily while over-taking the bicycle.
Even if the cyclists keep to the side of the road, bigger vehicles like buses and lorries (that always travel on extreme left lane) will have to "eat" into the right lane in order to over take you. In turn, the vehicle on the right will need to step on the brake and slow down, so that the lorry/bus got enough space to overtake the cyclist. This will be a chain reaction as all other cars behind got to slow down or change lane, just because of one incosiderate cyclist cycling on the road. :nono:
Some more bicycles are so light and fragile, you may topple if a car speed past you. I always make it a point to horn at bicycle riding on the road, hopefully they will realise the danger before they got run over.