Although this post is very old (2001) I wanted to improve on this answer from "I Am Always Liable" regarding the third paragraph (underline added.)
In California law, Code of Civil Procedure 391-391.7 defines a vexatious litigant and the court's remedies available to curtail the fun they have at other's expense.
In § 391(b) defines a vexatious litigant as
(paraphrasing to save space) anyone who in the last seven years has filed at least five suits
in pro per (not represented by an attorney) where the person lost the case, or where the lawsuit was left open, without good reason, for at least two years without taking the required steps to proceed to trial. The vexatious litigant statute specifically excludes small claims cases from the required minimum total of five cases in seven years.
In California small claims courts, generally, filing over 12 cases in any one year only results in paying a higher filing fee to the court clerk when filing additional cases.
This is not to say that the small claims court could not declare someone as vexatious if they filed only six losing cases, but if that happens it should be grounds for appeal since it appears to not be supported by this statute.
Source:
WAIS Document Retrieval
The fine print: I am not an attorney. Your mileage may vary.