[wladimir]

I've seen this mostly as workaround for broken source control systems, along with a change log at the top of each file. For example with ClearCase it can be a hell to find out preceding revisions of a file (the tools are slow and very user unfriendly), actions that are trivial with more modern systems.

I tend to agree more with coding guidelines that go exactly the other way: Do not leave around any commented out or dead code. It breaks the flow of reading the code and can cause confusion as to what is actually happening. If you need to refer to an old state of the code, just provide a commit id in your comment.