This isn't simply wild speculation brought on by lack of a world-shaking product announcement: Two years ago, Jobs underwent a successful operation to treat a rare form of pancreatic cancer.
And having attended the keynote, it did seem odd to me that a showman as accomplished as Jobs would delegate so much of the presentation time to capable but less compelling Apple speakers.
So I e-mailed Katie Cotton, Apple's VP of worldwide corporate communications, to inquire about Jobs' health.
Her response: "Steve's health is robust and we have no idea where these rumors are coming from."
(I'm just guessing here, but perhaps the Zune marketing group?)