There is a bike lane on the Embarcadero all the way from North Point, and this section is a very well traveled bike route. Embarcadero turns into King Street, the lane continues then abruptly ends at Second Street. At this point there is a "Sharrow" painted towards the right side of the road.
What is a "Sharrow"? Let's go to Wikipedia
A shared-lane marking or sharrow is a street marking installed at locations in Australia, Canada, and the United States. This marking is placed in the center of a travel lane to indicate that a bicyclist may use the full lane. The name sharrow was coined by Oliver Gajda, of the City and County of San Francisco Bicycle Program, and is a portmanteau of share and arrow.
Another good pull is this...
Assist bicyclists with lateral positioning in lanes that are too narrow for a motor vehicle and a bicycle to travel side by side within the same traffic lane;
Now let's see what someone from the SFMTA - who is responsible for the design and maintainance of our streets - thinks about Sharrows
Jose said King Street's lone sharrow was painted on the right of the street because there's no parking there, meaning bicyclists can ride farther to the side without fear of being hit by an opening car door.
WRONG. The whole point of a sharrow is to indicate that in this instance, the cyclist is supposed to take the whole lane because it is too narrow for the motor vehicle and bike to travel side by side. If anything, the sharrow should be painted farther to the LEFT in order to preclude the cyclist from taking a cue from the marking to ride to the right in the lane that is too narrow for them to safely do so!
The photo at the start of that article sums up how Ms. Sullivan died. The cyclist is positioned side by side with a big truck on a road that doesn't support that positioning.