I don't really understand how this is legal. "Lane-splitting" is the apparent term for when motorcycles decide that the lines in the road are meaningless to them and swerve in and out between the rest of the cars.
"If there's room, then it's safe" is a ridiculous argument. There are two lines painted on the road that represent the lane in which a car is driving. Presumably that moving car has the potential to move side to side within that space, no? So while you might see that there's room for you up ahead, you have no way of really know that it will be there in the next 2 seconds. I'm not talking about opening the door because you saw the guy on the bike coming, I'm talking about just driving like you normally would. Whose fault would it be then? The motorcycle for trying something stupid? Or yours for not seeing him?
There's sure to be an audience of people that do this, that say "If you're against it, it's just because you're jealous that motorcycles can do it and you can't. Who made you traffic cop?" Well, wrong. On your way by you can hit my car. That bothers me. There's a certain level of expectation between the cars - I stay in my lane, they stay in theirs. I don't get too close to the guy in front of me, the guy behind me doesn't get too close to me. It's a mutual thing. Then along comes a motorcycle who in essence is saying, "Nono, trust me, I'm a better driver than you all. I will do what I want. All the rules you have set up between yourself don't apply to me, so you have no way to anticipate what I'm going to do. But watch out for me anyway because if you get in my way you must have done it on purpose."