I've always thought it sounded like a good way to get killed but that's just my .02
It's probably not the right technique to use if you're riding a Goldwing or any bike with significant width. But statistically speaking, it seems to NOT be an unsafe thing to do. Well, I mean you're already riding a motorcycle, and about 99% of Americans think you're already an idiot for that.
I can't say that I've split a lane as every time I was in California and saw others doing it, I was riding something that I deemed as being too wide to try it. I was tempted when I was passed repeatedly, but I resisted.
Ok...there was the time I was going through Yellowstone and traffic was stopped in both directions. When I saw bear cubs in the woods and people out walking behind them trying to get photos, I split down the middle of the two lanes to get away from what I evaluated to be a hazardous situation. If/when mother bear came out to rescue her cubs, I didn't want to be the first thing she saw as I sat there unprotected on two wheels.