As a cyclist in San Francisco, I feel as if the city breathes a distinct biking culture. As long as you stay away from the "highways" of the city in Pine, Bush, Gough, etc, you find out fairly quickly what streets are safe and you stick religiously to them. It's a necessity to oftentimes be a jerk in order to make sure a car can see you and not run you over. And maybe if you're on your bike long enough, you'll find that your jeans becoming tighter and tighter.
Not until I visited Amsterdam did I realize what biking could look like in a city, a utopia for cyclists in an urban environment. Designated bike lanes with protected right turns. Racks and racks of bikes locked along sidewalks. Bike bells filling the city, politely asking pedestrians to move out of the way. On the totem pole of vehicles in Amsterdam, bikes are at the top, followed closely by scooters and cars, and finally pedestrians. One of the most bike friendly cities in the world, I envy the support that the city puts behinds it's bicycling community. It is the beginning winter and people have still been riding their bikes to get where they need to go.