AlyssaS - 5:13 pm on Feb 6, 2011 (gmt 0)

There is a large number of mostly smaller hobby type websites that have only AdSense but tons of unique content.

Agree, and what's more they don't make much from Adsense because their content is so good - they are usually thrilled to get a check for $100 a year.

Just because you are monetised by Adsense doesn't mean the site is bad.

A better signal would be looking at the placement of Adsense on the page.

Lots of those hobby sites have Adsense in the sidebar, or a single block at the top. The New York Times, the Guardian and other news sites, put their adsense at the bottom of their article or tucked in the sidebar (usually at the bottom).

The MFA spam sites though put the Adsense within the article. You typically get a couple of paragraphs, then an Adsense block, then another couple of paragraphs, another Adsense block and so on.

Anyone looking can tell an MFA from a normal site merely monetised by Adsense - but is it possible for the bots to evaluate based on placement? I don't know enough to even begin to say how they would go about it. I suppose it depends on how Google breaks up and categorises the page.