I started prefixing certain lines with the colon (:) in my org-files, because it is a convenient way to get "verbatim" behavior. It has advantages over markup such as =code= or ~verbatim~ in that it looks better, can be used with text that spans multiple lines, and actually ignores org-markup (for instance ~[[foo]]~ in org-mode will still turn foo into a link, whereas : [[foo]] will render verbatim).
The question that I have is this: is that a legitimate / intended use of the ":" markup? I haven't seen it discussed in the docs, and only found its existence when org-babel results blocks started returning lines prefixed with ":". I think having a general lightweight syntax for verbatim lines is very desirable, and if ":" indeed fits this role, it should be mentioned in the manual under "markup" (since it is a logical place to turn to when looking for verbatim/comment constructs). --Leo