POTENTIAL CONFLICT WHEN APCH CTLR CLEARING ACFT FOR VISUAL APCH TO SFO BEFORE ACFT REPORT ARPT IN SIGHT. OPERATIONAL DEVIATION. TRACK DEVIATION.

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ACR B ON VISUAL APCH TO RWY 28R OVERSHOT HIS FINAL AND ENCROACHED ON OUR FINAL. SFO APCH WAS RPTING 5 MI WITH FOG; SKY PARTIALLY OBSCURED. FLT VIS WAS AT LEAST 3 MI FOR ENTIRE APCH. THERE WAS A THICK HAZE LAYER ABOUT 1000' MSL; WHICH MADE THE APCH DIFFICULT (OR IMPOSSIBLE) TO SEE WHILE OUTSIDE THE MARKER (BRIDGE). HOWEVER; THE ENTIRE APCH WAS CONDUCTED WITH AT LEAST VFR MINIMUMS. WHEN ACR B (ARRIVING FROM THE E) WAS CLRED FOR THE RWY 28R VISUAL; HE APPARENTLY COULD NOT SEE THE RWY AND OVERSHOT HIS TURN ON SLIGHTLY. ATC POINTED OUT THE ACR B TFC (AND WE ACKNOWLEDGED IN SIGHT) ABOUT 5 MI PRIOR. ATC ALSO INSTRUCTED US TO CALL WHEN WE HAD THE SAN MATEO BRIDGE IN SIGHT. AFTER WE CALLED THE BRIDGE IN SIGHT AND ACR B IN SIGHT; WE WERE CLRED FOR THE RWY 28L VISUAL APCH (EVEN THOUGH WE DID NOT SEE THE ARPT YET). WE WERE ARRIVING FROM THE S. THE HAZARD IN THIS SITUATION WAS THE PARALLEL VISUAL APCHS IN MARGINAL VFR WX. THE 28L AND 28R RWYS ARE VERY CLOSE TOGETHER; AND EVEN WITH EXCELLENT WX; WING TIP TO WING TIP APCHS CAN BE TENSE. WE ALTERED OUR COURSE SLIGHTLY TO THE RIGHT (.1 OR .2 MILE) TO ALLOW ROOM FOR ACR B. SINCE WE HAD ACR B IN SIGHT CONTINUALLY (AHEAD OF US BY ABOUT 1/2 OR 1/4 MI); THERE WAS NO CONFLICT. BUT; THE POTENTIAL FOR CONFLICT OR COLLISION WAS THERE. RECOMMENDATION: ENSURE ALL ACFT SEE APPROPRIATE TFC AND THE RWY (NOT JUST ARPT) ON THESE TIGHT PARALLEL APCHS.