The effect of rumours on Apple's share price

John Gruber takes Duncan Riley to task over his story about an "$800 MacBook", which, of course, proved to be pants. I largely agree with John, although I still think that it's worth asking the question of who benefits from a rumour like that (it certainly wasn't Duncan), but it's worth putting to bed one of John's claims:

"Riley is the one and only source for this $800 laptop rumor, it wasn’t even close to true, and it is dominating post-event news coverage and quite possibly a significant factor in Apple’s stock price dropping 5 points on the day."

While it's true that after the Apple announcements Apple's stock dropped, it's worth remembering that in the aftermath of Riley's story, Apple's stock rose. Take a look at the chart and you'll see that on the 10th, when the NASDAQ was largely flat, Apple rose by five - something that could be attributed to Riley's story and the follow-ups by various analysts.

So, while the expectation of a cheaper product might have contributed to a fall in Apple's share price post-announcement, that fall simply wiped out the gain that the rumour had caused in the first place.