Seriously, you don't really believe that, do you? I mean think about it: for the cost of a trade fee, any average trader could sell 666 shares in the hopes of shaking more shares loose, and I'm sure some traders do, just to see who believes in that myth. MMs are smarter than using such a simple number as a signal. If anything, they might use some other type of figure such as all even or odd numbers, such as 246810, or 35791.
I've spent a lot of time watching for signals that precede a rise or drop, and one thing that seems possible is when I see several very unusual amounts trade, such as 16777 3x in a row.
News 
Market Data 
Discover 
