In the California driver's handbook, it's called "lane sharing" and although legal it's not recommended. I can't remember the exact terminology, but it's something to the effect that lane sharing is legal between a motorcycle and another vehicle only when it is safe to do so. This determination is at the viewing police officer's total discretion. I'm pretty sure that if you're splitting lanes at anything about 15-20 mph, you will raise the eyebrow of your local traffic cop.
I lane share all the time when traffic is stopped or moving at a snail's pace. I have found that most people will make room for you but there are those few that for whatever reason decide to move over and not let you through. When this happens, I find it quite satisfying to go behind them and pass them on the right sided of their lane which has been left vacant because of their attempt to choke me off. Then, as soon as I pass thier car I move back over to the left side of the lane and continue on till I encounter the next trouble maker.
All perfectly leagal as I'm still "sharing the lane" with the vehicle at all times.
I lane share all the time when traffic is stopped or moving at a snail's pace. I have found that most people will make room for you but there are those few that for whatever reason decide to move over and not let you through. When this happens, I find it quite satisfying to go behind them and pass them on the right sided of their lane which has been left vacant because of their attempt to choke me off. Then, as soon as I pass thier car I move back over to the left side of the lane and continue on till I encounter the next trouble maker.