Mollom and human comment spam
In your article you seem to be confusing automated spam and normal people trying to advertise commercial websites through on-topic comments.
The problem I have been seeing for some time, (and Kris recently as well) is that normal people send on-topic opinions (or sometimes mangle the content with some general question) to make it seem as if they are part of the discussion. But they are deliberately leaving behind a commercial website that is unrelated to them personally or unrelated to the topic.
At first I was willing to keep those comments, especially the ones that added some value. But then I had to censor the URLs. In the end I did not want to encourage the practice and I decided it was better to moderate the comments out of existence.
I don't think Mollom is really meant to protect your from this kind of "spam", because it is highly unique. Mollom is very successful for automated spam though.
I also think that a simple disclaimer on top of the comment form would discourage most people making the (human) effort if there is a high chance of it never see the day of light due to moderation.
PS: I wanted to comment on your article, but I couldn't find any way to do that from your site :-/