i will take the lane in any instance where i do not feel that a car can share the lane with me and safely give me 3 feet of passing room. it also helps especially on low visibility one lane roads to let cars know behind you when it is ok to pass. a lot of drivers appreciate that.
i had an incident last week while biking in a downtown area of my neighborhood. i was biking on a 4 lane road (2 lanes each way) and was in the middle of the right lane which was not very wide. a van behind me honked impatiently, turned into the left hand lane and passed me only to stop immediately after at a red light. i pulled up next to the van and politely and calmly asked if there was any issue.
"YEAH, YOU WERE RIDING IN THE MIDDLE OF THE LANE"
"Well yes, but you see there are two lanes here. You could always move into the other lane to pass."
"BUT WHAT IF THERE WAS ANOTHER CAR RIGHT THERE?"
"Well then you could, you know, wait?"
"OH YEAH LIKE I CAN WAIT"
the fact that waiting for maybe 5 seconds was out of the question for this guy is both ridiculous and depressing. i don't recommend confronting drivers though. very rarely can you change their opinions of you.