[color=fff200]Semi-incoherent rant about to begin[/color]
As a proud NorCal Bay area kid, I actively try and avoid playing RPs set in the San Francisco Bay Area (or read/watch/play any media set there) because of how wrong everyone gets it. 
My personal take on it is that it's the entertainment industry. What two places have the highest collection of writers and actors? New York and L.A.
People write about what they know. People who live in these places will make movies about those places, because regionalism is alive and well. And so it gets shipped around the country, and then everyone watches it, and they learn of these places through the films or whatever.

And people aren't all that original, truth be told. So when it comes time for [i]THEM[/i] to make an RP/book/film/whatever, they'll be inspired by the last movie they saw, and think that New York/L.A/SF are the cool and mysterious places, and then they'll set the story there. 
Last time I played a game in the SFBA, I ended up making a map to show the spatial relationships between everything, because goddammit people it's fucking impossible to get from Stanford to Napa without preparing for a year long journey through traffic. 
Or people will ignore the existence of Oakland (unless it's a crime show, in which case they'll ignore the fact that much of Oakland is just nonviolent suburbs) . Or they'll fail to understand that Marin county is what's on the other side of the Golden Gate, and only mention the charming little town of Sausalito, because that's directly where the ferry runs to, so that's what they'll see if they go on a tourist trip.
The list goes on and on. I personally find it really hard to play a game anymore that is set in the contemporary and real world, because the knowledge that I am so grandly fucking up the geography of that place is too much for me to bear.

TL;DR:
People like to talk about where they live. The two main centers of global entertainment are in NYC and California. The people who live there like to set stories where they live. Those stories are shipped across the world. There is now a meta-narrative about these places. People from elsewhere, wishing to have work viewed similarly to mass media, will imitate them in setting. And this causes a lot of amusement from the people who live there, because they will horribly, horribly fuck things up, because they are not from there, and have no clue about what it's actually like. [b]SO SET YOUR CONTEMPORARY RP IN WHERE YOU LIVE.[/b]

ALSO: Anyone who refers to San Francisco as 'Frisco' is a disgusting tool who deserves to die a peasants death.

[color=fff200]Rant: END[/color]