Sure, this year’s conference lineup featured CEOs from more large companies than in years past. Microsoft’s (MSFT) Steve Ballmer, eBay’s (EBAY) Meg Whitman, AT&T’s (T) Randall Stephenson and News Corp.’s (NWS) Rupert Murdoch all took a turn on stage. (On the first day, co-host John Battelle noted the star power, saying, “In past years, we couldn’t even get these guys to call us back.”) But conference goers mostly wanted to talk about the company with the 23 year-old founder who pioneered the concept that has become this year’s buzz word: the social graph.

Just what is the social graph? On Wednesday afternoon when Facebook’s Mark Zuckerberg joined Battelle for an onstage interview to open the conference, he defined the term: “It’s the set of connections that a person has in the world.”

Even as Zuckerberg spoke, the conference was abuzz with speculation about news of an impending partnership with one of the Internet behemoths, Google (GOOG), Microsoft or Yahoo! (YHOO). In his interview, Battelle grilled the stoic CEO about a possible sale of a small slice of his company. When asked how they were coming, Zuckerberg responded in his predictably monosyllabic and nearly monotone manner: “Great. It’s almost wrapped up.”

Meanwhile, in the conference hallways where the real action takes place, entrepreneurs, investors and journalists frantically exchanged final notes on their latest projects. What’s the hottest idea floating around this year? “Facebook, definitely,” one entrepreneur told me, flipping open his laptop to show me an application he was designing for the site. And what’s the most over-hyped idea? He didn’t skip a beat: “Facebook.” Take note.