Google is facing its third and probably not its last court appearance this year over click fraud, after the filing of a new class action lawsuit in Pennsylvania.

Samuel Lassoff, the owner of two US websites, has accused the search giant of exposing publishers to click fraud through a breach of contract, negligence, unjust enrichment and unfair business practices.

Filed on August 10, his class action follows Google’s $90 million settlement with web publishers in May – which Lassoff said was insufficient – and the filing of another lawsuit in California in June.

Google made a settlement that was ridiculously unfair to publishers, and anyone who was involved should be appalled,” said Lassoff, as quoted by Google Watch. “I still think a lot of businesses don’t even know they were defrauded.”

Google has yet to react to the lawsuit, but a spokesperson said: “We’ve dedicated expert engineers to it and believe that the problem is small and that we manage it well. This lawsuit is without merit and we will defend against it vigorously.”

Although a decision is yet to be made on what exactly constitutes click fraud, “small” is possibly not a definition many advertisers would accept, considering this Click Forensics study here.

Chris wrote an article on the issues of how to identify click fraud in June which explains the difficulties of measuring, defining and dealing with the problem.

You can also read the thoughts of Google CEO Eric Schmidt on the economics of click fraud and there’s something called the Anti-Click Fraud Alliance that aims to figure out how to better measure the problem.