What a way to find out. http://gizmodo.com/5120687/steve-jobs-health-declining-rapidly-reason-for-macworld-cancellation
Funny all they have is a "solid source" and then go to such lengths to legitimize it. This is probably like the manipulation of AAPL during the options dating scandal.
Actually Gizmodo is one of the most popular/legit sites on the net - I don't think they would risk a lawsuit to make a few dollars off manipulation.
I don't know how lawsuits work, but they could blame their source. And plus popular blog is one of the main ingredients for getting the rumor as wide spread as possible. We'll see.
If jobs really is gravely ill I would think the news would be out simply because it would be difficult to keep something like this under wraps because all eyes are on jobs. I could be wrong though.