I'm working on a new programming language, which determines structure with indentation instead of braces in the manner of Python and CoffeeScript. Obviously placing lines indented with spaces next to lines indented with tabs will mess up that kind of syntax, so I'm disallowing that - any given source file must use one or the other, not both.
I'm wondering whether it would be better to mandate one or the other across the board just to eliminate the possibility of time wasted on argument? Spaces seem to be slightly more popular than tabs, so if I were going to do that, I suppose I would mandate indenting with spaces (despite the fact that I personally prefer to use tabs).
Are there any situations where eliminating the possibility of indenting with tabs, would cause a problem?