Lane widths vary wildly, even in California. In SoCal, the lanes are hugely wide, much wider even than in the Bay Area. BUT, then in some places, those super wide lanes don't exist, so splitting has to be done very carefully, if at all. As for the idiot in the left lane, that's where I just go past them.
Wallowa, I appreciate your opinion, but please don't hamper our attempts to legalize it. Just because you don't think it's safe doesn't mean it isn't. I started riding BECAUSE of lane splitting. And from there it turned into a passion, and now I commute daily by motorcycle, even up here in cold, wet, rainy Oregon. I do occasionally split up here, and most of the time, people don't even notice.
Something you learn as a splitter is to watch for cars that may make sudden moves. It becomes a sixth sense. I have never been surprised by a car doing something stupid, whether splitting or not... why? Because I've anticipated it. Even the few times cars have tried to squeeze me (whether intentional or not), it's not been a big deal, because I always have an out. Any good rider will always have an out.
'12 Suzuki V-Strom DL650
'96 Suzuki DR650
'10 Kawasaki KLX351S #320