Most software projects with more than one programmer seem to enforce some kind of formatting style for the code - brace positions, indent width, use of tabs - that sort of thing.
At Microsoft, we didn't spend a lot of time talking about the style but we did have one rule - you should try to make your code consistent with the code around it. (If you were in the fortunate position of starting a brand new project from scratch, you got to choose the style yourself.) At least until the tyrannical StyleCop showed up. I left before using it for very long but I hated having to placate it (especially when I disagreed with its rules - for example, it wouldn't let me insert extra blank lines to group related functions, or arrange my functions in a more logical order than the standard one).
The GNU coding standards are similarly strict. I haven't disagreed with them very much (though I dislike the convention of having two spaces after a full stop).
I suppose having style guidelines (provided they are good ones) does make the source code look prettier and more consistent. However, I'm not convinced that it is worth the effort, especially since any programmer will have to be able to read code written in any style anyway (lest they start making assumptions and get fooled by a malevolent patch). In fact, there may be certain benefits to allowing every programmer to adopt their own personal favorite style. For one thing you'd be able to tell at a glance just who wrote any particular piece of code in your program (assuming that there were a small number of contributors and you're familiar with all their work, which I don't think are particularly bad assumptions in many cases).
Programmers' personal style also changes with time, so this can also be a good gauge for how old a particular piece of code is.
However one chooses to format their code, it is important that is readable - not having indentation at all, or having inconsistent indentation in a given class or file, or having indentation that misleads you about which "if" an "else" is paired with should not be acceptable.
One might get the impression from reading the above that my own preferred coding style is not particularly consistent. Nothing could be further from the truth - I've spent many hours (probably far too many) reformatting code to my own personal taste (K&R style with the exception of putting opening braces of global functions and classes on column 1) to make it look prettier. I used to prefer indenting by 2 spaces but now I prefer 4 (a habit I picked up at Microsoft). As I like to avoid very deeply nested constructs (and like to be able to see how deeply nested I am easily), I may even increase that further in the future.