I wonder if this law still makes sense. I feel it could be altered to say that recording someone without them even knowing you are listening should be illegal, but I don't see why it should be illegal to record a consenting conversation between two people.
Generally the laws on video recording are based on where the camera operator is standing while filming. If you have a lawful right to be where you are, it's probably ok to make a video. But take a look at the facts in Shulman v. Group W Production, Inc. (1998) 18 Cal. 4th 200, where the camera crew was lawfully present but intruded on a private encounter. Very much depends on context, at least in California.
Btw, does it apply to video recording as well?