Bus Lanes
There seems to be a trend of allowing motorcycles to use bus lanes; Plymouth began shortly before I started cycling, and it seems to be the norm in London too. I actually find motorcycles more offputting than buses or taxis when I’m cycling (though I have other complaints about taxis). Buses and taxis will generally overtake a cyclist properly, moving well to the side (traffic permitting), and so they don’t present any real threat; conversely, motorcyclists tend to try to share the lane with cyclists, which means they’re passing relatively close and often at full speed. There’s not much that’s more offputting than the sound of a speeding motorcycle approaching from behind in an otherwise empty lane. (That’s quite aside from their tendency to use cycle lanes and advance stop zones, even more frequently than other drivers do.)
My objection to taxis, particularly black cabs (in London) is more political. In central London, inside the congestion charge zone, cabs make up a significant proportion of the traffic anyway, and I don’t see any particular reason that they should have special privileges — it’s not like they’re any better for the environment than any other car. For most journeys, people should be using trains (mainline or underground) or buses, and the only people driving or being driven should be those who aren’t able to use public transport — not simply those who are too lazy. (Conversely, I see no reason why blue badge holders shouldn’t be allowed to drive in bus lanes, since the reason they’re driving is that they’re unable to use public transport.)