Twitter love was in full bloom at the Web 2.0 conference on Wednesday, with Microsoft and Google each announcing deals to partner with the microblogging service.

But marring the Twitter hoopla were no-shows from two of the event’s highest-profile speakers.

A day after Yahoo CEO Carol Bartz skipped the company’s quarterly earnings conference call (because she had “come down with something” as CFO Tim Morse explained), Bartz skipped the Web 2.0 conference, where she was scheduled to kick off Wednesday’s events with a 30-minute talk.

Web 2.0 organizer John Battelle told the crowd Bartz had come down with “a very, very, very bad flu.”

Before the day was through, Battelle delivered news of another absentee.

New York Times Chairman Arthur Sulzberger, Jr., slated to be part of a panel on the future of journalism in the online age, was also hit by the flu, Battelle said moments before the panel began. Fortunately, Martin Nisenholtz, the New York Times head of digital operations, was there to stand in as Sulzberger’s second.

With one more day to go, attendees at the event are hoping no one else gets afflicted.