Mike Arrington has published Comscore’s most recent numbers for Facebook’s traffic and last month Facebook attracted 115 million visitors. MySpace attracted the same amount. At least that’s what Comscore and Techcrunch are now reporting. How many users does Facebook say they have? Over 80 million. That means 35 million visitors to Facebook last month do not have accounts.

If you take a look at Alexa’s chart of Facebook versus MySpace traffic (as pictured below), Facebook had already surpassed MySpace in traffic. So what’s the real story behind these conflicting numbers? Well, one rationale is that Facebook is purposely understating their user statistics which would make a lot of sense.

Currently Facebook claims that they have around 80 million “active users” which means that they “returned to the site in the last 30 days.” The wording of that phrase could be misleading though. Theoretically there could be 80 million that returned and 35 million that registered last month alone. That seems a little ridiculous though. Given that Facebook is attracting at least 250,000 new users a day we know that at least 7.5 million people registered for the site last month alone.

That would leave another 27.5 million visiting the site via links around the web. This is definitely possible but if it’s true, that means that Facebook has a 21 percent conversion rate of new visitors into new users which is an impressive number. It also means that Facebook is now beginning to rely increasingly on search traffic to generate new users registrations. Whatever the case, Facebook continues to grow extremely fast and may now be the largest social network in the world.