Lane Splitting is the process of riding your motorcycle in the same lane with cars or other motorcycles. Normally it is done at low speeds with cars stopped or nearly so. California is a state that does allow it mainly because the California Highway Patrol motorcycle cops, CHP, do it. California regulations say: "Lane splitting by motorcycles is permissible but must be done in a safe and prudent manner."
Reading through the responses, I'm glad I'm not splitting lanes near some of you,

. I suppose it's the human driver thing of not wanting Anyone to "get ahead" of someone else...
Legally, only a couple/states permit it, from memory. I've done it a few times on the LeftCoast, (legally), and a few times in other situs where it's not permitted. I found it effective if moving at a slightly higher pace than the stop 'n'go traffic, and certainly allowed for forward progress.
Air cooled m'cycles and even some coolant-cooled sleds have a diff. time in long periods of stop and go, (our prob. not the car drivers' prob.); thus, the ability to carefully slip through at a reasonable pace, is appreciated and often done regardless of law.
The Squids and kamakazies out there doing a buck and a half through traffic...well, there are bad/agressive drivers in all kinds of vehicles.
This arm wrestle could one sided, by what I've read thus far, but the basic tenet of Everyone whom has ridden motorcycles safely for a few years, or longer, is that your basic car driver does not see us, does not care and pays little attention to "regular traffic", let alone the scoots on the road.
Not an Us against Them deal, but after more than 4 decades of riding on the street, the "average" cage driver, (or even above avg. one), is Not my "friend", via their actions and lack of attention while on the road

.
Lane splitting: not legal in nearly all states; sometimes done when conditions warrant the risk. Not for the faint of heart and requires max concentration. But, should not be an action that brings about car drivers trying to injure or kill the m'cycle rider whom jes' split your lane, imo.
My fiftyScent is up. Keep an eye out for sleds, please.
BR,md