Speculation is rampant about what's really going on with Steve Jobs, after Apple abruptly announced today that he won't give his annual keynote speech at next month's Macworld conference in San Francisco.

Apple said its senior VP for marketing, Philip Schiller, will speak instead and the company won't participate in Macworld in the future. So much for the big counterweight to the Consumer Electronics Show taking place the same week.

It also makes me wonder if Apple was the source of rumors this week about the company introducing low-cost netbook-type Macs at Macworld. Could that have been an attempt to keep expectations high despite Jobs' absence?

But Friday Harbor tech pundit Mark Anderson sent a note to his newsletter clients this afternoon that sums up what manyt Apple watchers are probably thinking: That Jobs -- who has battled pancreatic cancer -- is sick again.

There are at least two ways to take this: a cutback in expensive physical presence at a time when everything is going online; or Steve is not looking good physically, and is unwilling to go through the intense examination of his health condition which occurred after the last Macworld.

Unfortunately, I don't think the first is the correct choice.

The final decision here may become clear when the speaking agenda for the Apple WorldWide Developers' Conference is made public.

But I cannot think of any reason for Jobs not to appear at the next Macworld, regardless of new strategies, other than his health.

Apple was down about 3 percent to $92.88 in after-hours trading.