Facebook founder Mark Zuckerberg is facing a suit that could cost him billions if a judge finds that the documents presented so far are genuine. So the first question is whether they are or not.

Paul Ceglia filed a lawsuit against Zuckerberg in July, claiming that he had paid Zuckerberg for some web development work and invested $1,000 in the then-nascent Facebook in exchange for 50 percent of the business.

Zuckerberg's lawyers claim the emails and the contract in the complaint are simply fakes. Outlined below are the major arguments for them being real, and why they might not be.

1. Fraud would put Ceglia in jail

The authenticity of the documents - a set of seven-year-old emails and a contract - will be addressed in the discovery process as the lawsuit progresses, if it does. If the emails or contract are found to be fakes, then Ceglia could be charged with perjury or fraud as well. Either one carries a risk of jail time. It is difficult to imagine Ceglia thinking that a company the size of Facebook, with its attendant ability to afford legal talent, would simply hand him money without a fight.

2. DLA Piper's due diligence

DLA Piper is a well-respected law firm, one of the largest in the country. The attorney on the case, Robert Brownlie, said he has spent part of his career defending against lawsuits similar to Ceglia's. A law firm or lawyer knowingly taking part in a fraud would be subject to significant sanctions and possibly disbarment. DLA says it did due diligence and was willing to take the case, likely on a contingency basis. That means the lawyers who have a great deal of expertise think they can win, or at least get a sizeable settlement.

3. Facebook non-denials

Nobody on the Facebook side has denied that Zuckerberg did the relevant work for Ceglia. Which means at the very least that until they give an unequivocal no one has to assume that the two had some kind of business relationship.

Those are two big reasons the emails and contract could be real. Here are the reasons they might be fake:

1. Ceglia is already accused of fraud

Ceglia is facing a fraud indictment from the state of New York, relating to a wood pellet business he had in which customers complained they didn't get their pellets. While that can't be used in evidence in the civil suit, it does show he is no stranger to scams. He may just have picked an exceptionally large one.

2. Why wait?

The emails show Ceglia is business savvy enough to know that any site needed advertising or paid users. He even suggests ways to make money. Yet just after an exchange in which he tells Zuckerberg to take a f---ing ethics class and accuses him of essentially walking off with his money, he took no further interest in Facebook. Facebook was a runaway success years ago - by 2006 the company opened the social network to anyone over 13, and a year later Microsoft invested some $240 million in the company. Ceglia says he had forgotten about the contract until his fraud indictment prompted him to search through his records. But Facebook had become a phenomenon by 2006, and it is tough to see how Ceglia could have missed that.

Could Ceglia fool a law firm as sophisticated as DLA Piper? Yes, it is certainly possible. Could Ceglia be unsophisticated enough to forget about a contract with one of the most famous people in the world? Possibly.

The next steps will be crucial for both sides. The discovery process will determine how authentic the lawyers for Zuckerberg and Ceglia think the emails are, and what they can prove. If Ceglia can produce a cancelled check to Zuckerberg for the $1,000 that lends much more credence to his story and could very well drive Facebook to settle. If Zuckerberg's attorneys can show the documents are frauds - or at least of doubtful authenticity - then DLA Piper will be out a lot of money and Ceglia may foot the bill, if he isn't jailed.