1. I find it rather funny, and fitting that San Francisco is actually under a state of emergency because of this... San Francisco City/County, being about a 4 hour drive away from the fire, gets 85% of it's water, and much of it's electricity out of the north end of Yosemite NP. John Muir still gets the last laugh.
2. I didn't read much of the arguments going on in the thread, but let me just say this much, the areas where fires are burning out of control in N. California and Oregon have been sparked naturally by lightning, and left to thicken naturally as well. This poses a very natural problem, that humans are still just starting to understand.
3. That problem is that when forest stands are left alone, to thrive and become extremely thick, they are very prone to catastrophic wildfires. National Parks and Wilderness areas, and the general region around them, tend not to be forested in any way/shape/form. You get saws within an hour drive of a USNP, and the Sierra Club will FREAK OUT, and legislate the fuck out of you for 30 years... within that time, chances of shit like this tends to become ever increasing.
4. The area in direct question, has not been thinned in god knows how long. With strong winds, heavy thunderstorm activity this summer, and fairly dry conditions after 2 very dry winters, you can only expect this sort of thing to happen. This same exact thing could be easily seen at many other national parks.
5. Don't worry folks, the main valley floor of YNP isn't really threatened at this time. The fire is headed mainly north/northeast, away from that area. It could spread if things get insane, but as of right now, only the north end of the park is in serious danger - not that that's really a good thing... Still worrisome, indeed.
Have a nice day, Bluename.