I was in a car with a friend. She drove so close past a cyclist that I was scared, but didn't realise it was uncomfortably close - she doesn't ride bicycles/motorcycles. People often just don't think - it could have been unintentional.
In my country, a pass like that is a rule of thumb, by the way. You get used to it. Even when taking the lane, they drive as if they'll run you over, then turn at the last second to pass, without slowing down. I removed my bar mirror, because it freaked me out - better not to see them coming.
What I do is make sure that my lane position is such I don't swerve to the left (towards the middle of the road) in order to avoid debris, holes etc. Move as far to the left as needed. I also make sure to leave some room to swerve to the right if trucks/busses swerve to the right as soon as the front end of their vehicle passes my front wheel.