A flat file is essentially a .csv holding data, and can be a fast way to bulk load denormalized data. As such, it actually does have a use in the context of scaling, so it's natural to expect that they were using the term correctly.
A static file, or more simple, a HTML file is what they're actually talking about. As they've noticed, it's what web servers are best at serving, and it scales obnoxiously well.
Now that we're all talking about the same thing, I can say that I've been serving all my product blogs as .html for years, and have never had any of them fall down under load.
It's really easy to get something in place to generate static files from a blog or CMS. I do it with:
- a 404 handler that maps missed requests for .html to their equivalent generator.
- a regular old blog engine that takes an extra parameter "writeThisToHTMLOnceYouveRenderedIt"
Future visitors skip the redirecting and generating and are simply served the static file. Next time you edit the content, you can simply blow away the whatever-blog-entry.html and index.html and know that they'll show up again next time anybody asks for one of them.