Depends on the area I am in. When I lived in the MD/DC suburbs, which are awful with traffic and no shoulders at all, I've had Metro buses brush by so close that their mirrors miss my head by mere inches. Since the roads are narrow, everyone passes me within 2 feet at slow speeds.

Here in DE, we have generous bike lanes, but that doesn't stop the occasional redneck in his raised Ram 2500 Quad Cab from slowly forcing me closer to the curb so that he can make his quarter-mile-early right turn. Most people give me plenty of room, just a small percentage want to show me who is the boss.