On a clear day in San Francisco, nothing is more beautiful than the 28L or 28R approach over the bay toward the city.  You can see everything the city has to offer and usually marvel at the aircraft just a short distance off your wing paralleling you on final.
This wasn’t one of those days.
It wasn’t quick thick fog, but the costal marine layer had set in and was disrupting normal visual approaches.
To accept a visual approach while on an instrument flight plan, the pilot must either have the airport in sight, or the preceding aircraft in sight, and maintain either item in sight until touchdown.
In this case our pilot picked up the aircraft ahead of him, but did not have the airport in sight.  A portion of the marine layer was sitting between him and the airfield.  Just passing 10 miles to the airport, the pilot lost sight of the aircraft 4 miles ahead of him.  Radio traffic was heavy and it was difficult to get a radio call in.
Just as the pilot keyed the radio to report he had lost the preceding aircraft, he gained sight of the airport lights and completed the approach.  He had lost sight of the aircraft he was following for about 30 seconds.
Was the decision to continue until a radio call could be made appropriate?
Should he have discontinued the approach immediately?
What was the risk to his course of action?
Did he break a regulation?
What would you have done?