I have been riding on the street for about 30 years. 150k or so miles. When I lived in Seattle, a Suzuki 550 was my only transportation.
I wear gear every ride- dress for the crash, not for the ride. I don't do wheelies. I don't dress like a pirate and go to the bar.
The key to safely riding is awareness. As stated above, ride like everyone is out to kill you. It doesn't matter how good of a rider you are, physics dictates in a collision with any car, the car will win.
Graveyards are full of bikers that had the right of way.
I have limited my in-town riding over the past decade or so due to the ubiquity of cell phones. I drove a 4000 pound truck and often feel unsafe in traffic. On a 400 pound BMW it can be terrifying.
Many people do not like riders, as evidenced by some comments above. The hooligan crowd, the loud pipes guys and others portray a selfish image that creates a negative image in many- including myself.
I ride quiet bikes. I was in a neighborhood and a little boy saw me coming and stuck his fingers in his ears. I felt bad for that kid. When I was his age, I would run up to motorcycles, not fear them.
That is my unnecessarily long winded way of saying lane splitting is a bad idea.
It will further the notion that riders are ego driven fools that have no respect for anyone else.
It is dangerous for the rider since many in traffic are angry and watching a motorcycle ride between cars can be a trigger for action.
Often times drivers will narrow the gap to stop the rider. There is always the prospect of winning a "door prize", or having a beverage or worse tossed at them.