Site manipulation for backlink relevance : discuss!

[jasonmorgan]

Those like myself will argue that a backlink from a site / page of relevant content is stronger than a random backlink.

I've always gone with the idea that if google feels that Site / Page A is relevant for Keyword A then a backlink with appropriate anchor text from that site will strengthen my own authority for Keyword A.

But, what I am trying to narrow down is: what elements on that site / page are used when determining relevance and can that site / page be manipulated to create relevance.

For example:

There are a number of sites (tv stations... hint hint) that allow you to sign up and create your own blog. I'm sure most of you know what I'm talking about.

Lets say I want to create relevant backlinks for Sea Monkies. I create a new blog post at this site and drop in an article about Sea Monkies with backlinks to my Sea Monkies site. The content I've added to this blog is the highest percentage of content on the page and technically the page should now be relevant to Sea Monkies, however, the site as a whole has little to no relevance for Sea Monkies.

This same technique could be used for blog comments or any place that allows you to add content.

I could even go one step further and create backlinks to that blog or site with Sea Monkies anchor text to further manipulate the relevance of that blog for my own purposes. It wouldn't be enough for that site / page to rank for the keyword (which I don't want anyway) I simply want google to think that the site / page has some relevance to my own site in order to get more backlink juice from it.

So.... what do you think?

Can a site be manipulated in order to create relevance to my own site and used as a means to artificially create relevant backlinks?

What am I not seeing, missing?