Picking the target audience sets the scope of the product, as it really defines what needs to be included, and excluded, when deciding upon what functionality to provide.
Having been born out of catering for a small site for one person, that target audience was a given, and is a large one. However, the next decision was about whether I would target only English or really take on world-wide use. Unfortunately, even now only a few languages dominate the web, so catering for a wider variety of languages, especially since UTF-8 had become the standard encoding of the web, seemed like a no-brainer.
Of course, catering for multiple languages meant I would need to provide documentation in multiple languages, eventually! The obvious was to make the product fit for that purpose, which automatically provided the second target audience of developers who want multi-lingual help for their apps. This is called eating one's own dog food which makes the product its own ad. There are a lot of nuances to this that I didn't appreciate at first, especially in relation to dealing properly with right-to-left reading languages, particularly when mixed together with left-to-right.
An extension of the single-person site paradigm is those run by one person but who might have others involved, such as for small clubs or publicity outfits. While larger ones would require a more complex setup than my product provides, most would likely remain small for their whole lifetime. Accordingly, I don't expect this audience to be big, but I have used it to shape some of the facilities provided, especially in the article life-cycle management across multiple languages.