In Canada it's illegal.

Bullshit. these guys are dead wrong. It's unsafe.
Cars don't stick to the middle of their lane. They drift side-to-side within the lane.
And some times they even switch lanes.

I'm too busy right now to write up a big rant why they're wrong - but that's my stance.
Yes, I do ride a motorcycle, and have for many, many years.

I await your rant...and I wonder as a motorcyclist, how do you protect yourself from being rear ended?

What a rubbish video. It's supposed to be about why (they believe) lane splitting is safe. It's 14 minutes long and they spend about 2 minutes actually talking about that.

CA lane-splitting rider here. I'm glad it is legal, and I'm glad I have the opportunity to decide whether and when I want to split lanes. If I feel a section of road will be unsafe, because of an often congested on-ramp for example, I can safely re-enter a lane and be a part of traffic. However in very congested/stand-still traffic, such as rush-hour or stop lights, I will gladly relinquish my spot in a lane and drive at a safe speed between traffic until I wish to or feel the need to reenter. I'm not saying it's safer in all situations, a la this video, but the choice should be there.

Anecdotal evidence from my experiences; I've been nearly cut-off more times while in a lane than between lanes. Of course I ride in a lane more often so it's not really a balanced comparison :]

End of the day; it should be up to the rider. It has to do with self responsibility, awareness of the risks involved and how to handle them.

(btw, I hate that they bring up asia....come of those countries don't even driver license requirements)

I wish lane splitting was legal, it's so frustrating when I look at traffic that I just can't get past simply because I'm not allowed to go between the cars

So there's been some fun reactions to this video and I have to share it.

http://hellforleathermagazine.com/2013/01/internet-reacts-to-lane-splitting-episode-of-rideapart/

As a car driver, I support it. Gets more people out of my way.
I like bikes getting to the front of traffic while I'm sitting at lights because they get off the line quicker than most cars do, and I'm not basing that on machine capability, I'm basing it on my observation that bikes appear to pay more attention and are usually ready the instant the light goes green (possibly because they don't want to get rear ended)

As for lane splitting being dangerous, yeah of course there's a potential for a very negative situation if/when people aren't paying attention or staying in control of their vehicle.. but then so is having nothing but a painted line separating you from oncoming traffic at 100km/h.
For any reason why lane splitting is bad, consider other driving situations by the same logic, if you have one that is notable (other than due to the lack of a crumple zone, as this is a trump card), then let me know.

I pay attention when merging lanes and use the indicator to signal before I start merging as it is intended, and have never had an issue or impact with bikes (or anyone for that matter). I also position my car either closer to the side of the road or middle of my lane in traffic to make it easier for bikes to get past, and it appears a decent amount of others do this as well.
Not sure if it's legal in Aus (I don't think it is), but I've never seen cops pull a biker over for it. Besides, it's efficient and if everyone is doing what they're supposed to (i.e. paying attention to their surroundings + controlling their vehicle well), then there shouldn't be an issue.

I'm interested in the reasons why it's bad or shouldn't be done, as I may be missing something from a bikes perspective.

@Sagemind, sounds like you may have other solid points, like the drifting and merging. I see these as issues, but my points are based on people supposed to be paying attention, controlling their vehicles (easier for some) and bikes picking their moments to dive through while not being rash about it.
Side note, I do see lots of cars and bikes behavior as being hard to judge and thus dangerous, if this is your main point, then I agree.

My first motorcycle (750 Magna), got it while living in California. When I found out it was legal to split lanes there I didn't feel so bad for having done it already. The motorists in California, I noticed quickly after having been driving in Texas for 23 years prior, are much more aware of, and courteous to cyclists.

Still, the douche-factor remains, had a few times where assholes pretended to open their doors or shout shit at you as you navigate a traffic clog-On some days, they'd get their instant karma in the form of, well, equally civil payback.

*related=http://videosift.com/video/passing-1000-cars-in-Bangkok-traffic-One-nigt-in-Bangkok

I never saw anyone get hurt in Thailand. But I know people who have!

passing 1000 cars in Bangkok traffic - One nigt in Bangkok has been added as a related post - related requested by deathcow.

i commute daily into work in london by motorbike, filtering is essential!