The ConnectU vs. Zuckerberg case is still open, but The New York Times reports Facebook’s real inventor, at least on a conceptual level might very well be another Harvard graduate, Aaron J. Greenspan, who established a Web service at Harvard, which he called houseSYSTEM:

An e-mail message, circulated widely by Mr. Greenspan to Harvard students on Sept. 19, 2003, describes the newest feature of houseSYSTEM, as “the Face Book,” an online system for quickly locating other students. The date was four months before Mr. Zuckerberg started his own site, originally “thefacebook.com.” (Mr. Greenspan retained his college e-mail messages and provided The New York Times with copies of his communications with Mr. Zuckerberg.)

So Greenspan (Aaron, not Alan) is claimant #3… but wait, perhaps it was Your Momma Nick O’Neill:

For all those that think they came up with an idea similar to Facebook before it was launched: congratulations! Unfortunately you didn’t have the same luck or resources that Mark Zuckerberg had at the time. Oh and by the way: I was one of the founders of Google. Just thought you should know.

They will all have to fight it out with Pete Cashmore, though, whose claim dates back to 1997:

I can only conclude that Zuckerberg used a mind-reading contraption to literally steal the idea from my brain. This will be the basis of my $1 billion lawsuit to be filed later this month.

But thoughts are not enough.. so Zoho CEO Sridhar Vembu’s claim may be stronger, since he has a Thought-ent (thought-patent) on it:

That very moment, his eyes lit up, and he screamed “Yes, YES, OMIGOD, Face on the book, FACE BOOK, I Got It, Now I Really Got It, That’s what I am going to do, Facebook. Thank you, Thank you, Thank you, I LOVE YOU!”

…So naturally I went to my lawyer, because I remember being told that is the first thing you are supposed to do in these situations. You know, like, billions could be at stake here.
He listened to my story intently, and started explaining the legal situation, in that measured, precisely crafted manner that I had come to associate with him: “Clearly you brought the two distinct ideas “FACE” and “BOOK” together in one sentence, on which the whole Facebook foundation rests, and which Mark Zuckerberg took from you, as proved by the reaction he had when the idea was transmitted to him. In legal terms, what you had was a THOUGHT-ent, also known as a thought-patent, which are considered legally equivalent to patents.”

(It’s a long but humorous post, I don’t even know which part to quote, you might as well read the whole story)

Last, but not least, my own claim:

I graduated in CENSORED when Mark Zuckerberg was likely in diapers. I really did not like our facebook on paper – I was seriously considering moving it on the Net. There was only one problem: the Internet did not exist. So first I had to invent it. Now you know: Al Gore did not invent the Web. I did.

Additional reading (claimants?): Insider Chatter, Mark Evans, muhammad.saleem, TechCrunch, Mashable!, Techomical and New Scientist Technology Blog.