Chart: An Apple flash dump

A snapshot of high-frequency trading algorithms in action on Friday

Source: Nanex Research. Click to enlarge.

FORTUNE -- What happened to Apple (AAPL) in the last minute of trading Friday?

Tyler Durden, who tweets as @zerohedge, offers the Nanex chart above as evidence that it was a premeditated flash dump executed by one or more high-frequency trading algorithms. How else could 800,000 shares worth nearly $300 million be sold in 17-second intervals?

If retail investors are moving back into mutual funds, per Sunday's New York Times, could it be in part because the algos have squeezed them out of what used to be their favorite stock?

For a backgrounder in how these things work I recommend Scott Patterson's Dark Pools: High-Speed Traders, A.I. Bandits, and the Threat to the Global Financial System.