[merijnv]

Oh, I agree that not trusting information on the internet is the sensible default. However, there are plenty of people who will be copying his examples directly without any investigation.

Some will probably post the exact same stuff on their own blogs or link to this post. Before you know it this example will drown out any serious search results for "vim filetype", effectively stopping new people from learning how to do things properly.

Now obviously this post is a bit hyperbole in this instance. But these things do happen because people can't be arsed to treat the things they write/publish with the care it deserves.