[...] In short, 8-char indents make things easier to read, and have the added benefit of warning you when you're nesting your functions too deep. [...]
Taken from Linux documentation (Doc*/CodingStyle) Chapter 1.
I think this explains very well the idea behind the 8-chars tabs "movement".
There are heretic movements that try to make indentations 4 (or even 2!) characters deep, and that is akin to trying to define the value of PI to be 3.
(The second quotation was just for fun :D)
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