It's inherently dangerous for both the rider and the guys in cages.

than I do sandwiched between two cars.

At least not here in NYC. I've was crossing on Houston one Friday night (it's a parking lot at that hour), merrily split up to the line at a red light...and didn't notice the NYPD cruiser at the front of the crowd until I pulled up right next to it. UH-OH…

Got a friendly smile and a wave out of them before the light changed and I took the holeshot. It's entirely reasonable practice if you're careful about it, makes two wheels by far the best way to get around Manhattan.

in town, I can understand it . . . but on the freeways, having a bike go between you and your neighbor is quite a shock

Then again, I have a water cooled bike, so I don't mind traffic so much as if I was rocking an air cooled.

make me think it is.

When I'm in my car, I want to know that area between the lane markers around my vehicle is not occupied by another vehicle. So when I'm not going to hit someone when I need to use that space for: Avoiding potholes, avoiding other drivers, avoiding road debris, looking around traffic to see the road conditions, effected by wind, effected by non-uniformity in the road surface.....

Lane splitting is as good as legal in Los Angeles.
I do it all the time ... sometimes right in front of the CHP.
They smile, nod and sometimes do it themselves.
But be careful! There's lots of crazy auto drivers out there and they just seem blind to us on 2 wheels sometimes.

It is legal in most of Europe and is not too much of an issue.

Here in NYC I do it at lights, accidentally pulled up next to the NYPD a couple of times and never been hassled - but I will not do it on the highway in a jam.

The fools on 4 wheels are just way too unpredictable up here, I've seen a large SUV abruptly surge across the lines to get his nose into a four-foot gap to force his way in a lane he THINKS may be moving 0.05mph faster, clearly not doing any kind of a mirror check whatsoever seeing as how I was about a car length behind. Shadowing the brake lever in traffic is a great habit.

The temptation to break a window was strong there, I'll tell you. I settled for blaring the horn and coasting by with a one-finger salute.

I rarely ride in NYC. I do most of my travels in the NY/NJ/PA tri-state area and I hear you. That said, I think that the rider should have the option. I cannot justify me sitting in traffic wasting gas, when I could easily filter around folks.

Hell, some cars think that they can filter. Was up in the Poconos on a crappy road, the right side of the lane was smoother, so I was riding to the right. Lady thought that meant she could pass me within my lane. Ran me onto the shoulder doing it. I had some choice words for her at the next light, that I do not wish to repeat.

I mean, it wouldn't fix the problem, but I bet it would vastly reduce the issue. There are still people who change lanes without looking, but the vast majority of drivers have been taught better - the same should go for looking on the lines in slow/stopped traffic.