Driving today, bus and one other car in front, four lane road. Bus indicates to pull into bus stop, I indicate and move into other lane to pass bus. Other car decides to pull out without indicating as I'm passing him. This leads to a blast on the horn and brakes being stamped on. Driver of other car starts to gesticulate so I put the window down. There then ensued a short rant from the other driver that since he was in front of me, he had right of way and I should have hung back to let him out first. The mind boggles.
Can be a bit of a tricky one - if someone is indicating I will usually screen for a moment to let them out if I can but if they aren't even indicating who knows what they are going to do.
In a related situation it is annoying when trying to pass slower or stopping vehicle in that kind of context if the next lane has traffic in it and then the people in the same lane behind you are clear to move over before you are and almost inevitably don't let you out - hence I try to move out early.