I’ve been having an interesting time experimenting with Google Adwords. (Given the, shall we say, “elite” size of my readership, I can assure you the goal is not revenue.)

Adwords recently has taken a significant turn for the worse finding relevant, valuable ads for this blog’s content. If you look at the Google ads in the sidebar to the web page, you’ll notice that all of the ads are generic “Get a free blog” ads, whereas two weeks ago they were less generic and at least somewhat related to the blog content.

The effect of this loss of relevance is clear in the numbers: the eCPM (effective cost per 1000 impressions) dropped almost 50% for the period of December 14-20 compared with December 7-13, from $1.04 to $0.58.

I’ve seen other blog posts complaining about similar adwords relevance issues and they’ve resorted to some fairly hacky things like moving non-essential content to iframes, but it’s not clear that would work here, or what else a blog author could do to impact relevance.

You might say that the issue is the range of topics covered here, but even the Berry 411 category is displaying ads for real estate and singles.

It gets weirder. The innovation category displays job ads while the Jobster category display blogging ads, despite lots of posts about recruiting and jobs.

Perhaps a clue is that the Berry 411 home page displays really relevant Blackberry ads. This could be due to the fact that the content is essentially static and singularly focused, which perhaps lets Adwords do a better job.

In any event, it’s clear that’s lots of room for innovation and improvement in contextual advertising and targeting.