Gunnar: Well, speeking of TeX: Why do I have to close \begin{document} with \end{document} then? But you are right that fixing the syntax by inserting a few closing braces and later fix the “little” details is convenient: Just fix the syntax first and see what the interpreter doesn with it to find out where the braces should actually be put. That’s often far easier than reading all the source to find the right place. Especially since most interpreters don’t point you to the place where you introduced the error but to the point where the interpreter decided it couldn’t get fixed anymore (often at the very end of the code or document source).
But when I program, I often use stuff like this (bash shell code in this case, since most readers should be familiar with the syntax):

for i in `seq 1 100`; do
  ...[lost of line]....
done # for i

This is to give me hints where certain loops end or at least should end. That’s also what I use indenting for: To give me visual hints about the program structure. But as said in my original post: I don’t think indentation is suitable to give the interpreter/compiler information about the syntactical structure of a program.

I’m wondering a bit why no Python user jumped at that assertion yet. I’ve not yet used Python myself, but as far as I know, it uses indentation as a syntax element.