As for bloggers opening up free wordpress blogs just for the sake of gaining a little traction…well, when put like that it sounds a little spammy! Yet done in the right kind of way with good short posts then yes of course, it could help. There are other authority laden domains that allow users to create content, which ranks for keyterms in search engines. People use these in similar ways too. Its all about leveraging the authority.

In terms of leveraging the authority of an en existing high ranking domain that you own already, I’d say that you wouldn’t have to go the sub route and that a standard directory folder would serve equally as well.

I need to add too of course, that your time might be better spent writing good posts too and commenting on other blogs and what not! Generally speaking its not too nice to be exploiting other domains simply because they exist. Yet the reality is that people will.

A determined results focused SEO with limited resources will generally use all the tools in the box to achieve their aims. The box in this case of course being – the thing we call the Internet