Cons: The board featuring San Francisco-specific reviews is a relatively low-traffic bulletin board. Searching too quickly enables "flood control" which disallows you from searching more than once every 20 seconds. This can be frustrating if all of your searches are returning zero results.
This site seems to be best for browsing, rather than viewing information about a specific restaurant.

EGULLET
eGullet is a deep bulletin board community which has many food specific forums. The eGullet society often features week-long question and answer sessions with food celebrities such as Ruth Reichl, Mario Batali, and Harold McGee. eGullet groups all California reviews together on one board.
Pros: Fairly active California community. While restaurants you are looking for won't always be on the boards, you are likely to get a response if you ask a question. eGullet is a non-profit organization and receives funding from paid subscribers and sponsors. This means no desperate pleas for money -- they seem to have a sustainable model running.
Cons: eGullet log-in process requires name, address, phone number, and much more information than most bulletin boards. Log-in required for posting or for a search using the eGullet engine. San Francisco restaurant discussion doesn't seem to be as deep as other sites.
While it is possible to use eGullet for information about the local restaurant scene, I find it best for boards such as Food Media and News and the Q & A sessions. Information while travelling overseas is also often helpful. eGullet proved invaluable for information about Venice, Italy when we travelled there last year.

CRAIGSLIST FOOD FORUM
The Craigslist Food Forum is highly active, but rarely on topic. This lightly administrated board allows any food topic on this board, so restaurant reviews are mixed up with topics such as "sushi rolling lessons."
Pros: If you are a free-form type of user who doesn't like breathing-down-your-back administration, then this is the board for you. It's active enough that most queries are answered.
Cons: Restaurant-specific conversations seem to comprise less than 50% of the board topics. Users are often a little abrupt and quick to criticize.
I would recommend this site for uber-geeks who are used to a stripped down forum format. Like mouthfuls, I would recommend this site more for browsing or for asking a direct question, rather than for searching for a specific restaurant.
Next Tuesday look for reviews of:
CHOWHOUND
CITYSEARCH
YELP