In some email I received from Ian Dall, sie wrote:
[...]
> I can't help but think that 8 spaces was based initially on lazyness.
> In the days before smart editors, tabs were a lot easier than counting
> spaces. The original reason no longer exists and the likelihood of
> such a pragmatic decision being anything near optimum for other factors
> seems slim to me.

Another good rule of thumb is that if your indentation is such that you
cannot `squeeze' meaningful code on the right hand side due to lack of
columns (limitation is 80) then the code needs to be restructured.  If
the indentation were reduced I'm sure some would still say this is true
(>:-/) and I believe the result would be more heavily indented code
until someone became sufficiently annoyed with the restriction of 4
spaces and wanted 2, at which point the code would be next to unreadable.

What about 6 spaces for indents ?  Why this power of two thing ? :)

Darren