My observation of San Francisco (admittedly genralization) is that the power neighborhoods generally hug the northern part of the city's shoreline. While successfully bridged for over a decade, Market Street was always a line that separated power (north) from what was one of the most depressed parts of town (South of Market, today's Soma).
North of Market from the downtown area to Telegraph, Nob, and Russian Hills and westward through the Marina, Pacific and Presidio Heights and out to Sea Cliff on the outer Golden Gate has long been associated with the main belt of power San Francisco.
I would also suggest that the highest peaks in the city that dominate its midpoint (Twin Peaks, Mt. Davidson, Mt. Sutro) set off the most middle class neighborhoods of the city to the west (i.e. Sunset, Richmond, Parkmerced, etc.) from the rest of the city of the city to the east.
East of this range of peaks, areas to the south of Market (Mission, Hunters Point, etc.) teneded to be the most blue collar portions of SF.
SF's own unique gentrification that has changed the nature of the whole city has, of course, poked a lot of holes in a lot of the observations above, as former middle class/blue collar areas (i.e. Noe Valley) have transformed to upscale neighborhoods and as SoMa, Mission Bay, South Beach,the ball park, expanded Muni, and UCSF radically change the concept of areas south of Market that have been sucked into downtown.