The northern cluster of >60% precincts is the whitest part of the city (over 80% white), and appears fairly wealthy as well.
The southwestern cluster is also mostly white, but more in the 50-60% range. It appears a little more suburban in nature (detached homes) and definitely on the wealthier side.
The central western cluster appears to be the Sunset District, and the most Republican part of it seems correlates with the most heavily Chinese part of the neighborhood. I'm not familiar with SF enough to know if this means it is the Chinese who are (relatively) Republican, or if they're more recent arrivals and an older white population makes up a very disproportionate amount of the vote like they do in many communities. Given that the Chinese-American community is well-established in SF, the latter explanation doesn't seem as likely. We don't see the same Republican cluster in the older Chinatown, but it may be more dominated by non-voting immigrants allowing other groups to keep it more Democratic. It also depends on what kind of Chinese live there --- Asian immigrants who left primarily to avoid Communists are much more prone to conservative politics. Perhaps some of them clustered in the Sunset District? Just a guess.
The >90% areas are generally the stereotypical hippie and gay areas, as well as the mostly black areas like Hunters Point in the SE.
Seattle is somewhat similar to SF. Both are West Coast cities that give similar percentages to the Democrats, are the two gayest cities in the country, and have similar economies. One major difference is that SF is less white than Seattle is. Still, in Seattle the most Republican areas are definitely the wealthier white neighborhoods, which doesn't seem as true in SF. Seattle has some conservative Asian areas, but it appears to more closely correlate with the Vietnamese population than the Chinese population. Gay marriage fell way behind Obama in heavily Asian areas. Given how prominent the gay community is in SF, and their association with the Democratic Party, it may turn off some more socially conservative/moderate Asians from the Democrats there. Though that's probably kind of obvious.
The northernmost, white part is the wealthiest part of the city as has been said, and is more yuppie than hippie. I didn't enjoy going out as much in the Marina as I do in the Mission. Way more douchebags around. And no Mexicans randomly showing up at 2AM to cook hotdogs.
The reason for Chinatown voting so Democrat and the Sunset not voting as Democrat comes down to income, imo. Chinatown is more low income, and full of more recent immigrants who don't have many marketable skills. The Sunset on the other hand is wealthier, the Chinese who live there are more established, and the area has more of a suburban feel.
