The clearance for the visual at SFO includes a restriction that you not pass the aircraft you are cleared to follow and to keep in sight. Sometimes NORCAL approach sets one up for an especially exciting experience by saying "Maintain visual separation on that aircraft, maintain 170 KIAS to the bridge, cleared for the visual approach 28L (or 28R)". So at the bridge you are fast and the airplane you are following is already slowed, and getting from Flaps 5 to Flaps 30 or 40 seems agonizingly slow while one still attempts to stay within "Stabilized approach parameters."
I too have gone around on that one. What I should have said was "Unable 170 KIAS to the bridge, cleared for the visual 28L."