The problem with creating pretty HTML that’s indented nicely is that it’s a language that can’t really be indented! It sometimes have an affect on the actual look of the page.

For instance with a <pre> tag, trying to indent that nicely with the rest of your page will make the output shifted massively to the right. The only way to fix it is to have the pre tag the only piece of the source that isn’t indented, which looks uglier than having no indentation at all.

Which inefficient weirdos are debugging by looking at their source and not using Firebug anyway? In your editor you should have “highlight matching tags” turned on. It adds completely useless characters to the page, which are literally invisible. You’re paying for those bytes, and the user is being made to wait fractions of seconds (which Google ranks you on) longer.

Just stop doing it!