1script - 2:58 pm on Mar 28, 2010 (gmt 0)
@tedster: Yes, the spam gets there via usual post submission mechanism. I filter what I think is 75% of it but some does get through. It used to be relatively simple: don't allow posts with an unreasonable amount of URLs and stop words in them. But spammers are always adjusting (their job, right?) and the most problematic recent type is a post with just one URL and a hole bunch of keywords that are relatively close to the theme of the site. It actually works against me in two ways: I'm more likely to miss it and then, it may start ranking because of those stuffed keywords and I could suffer a penalty for keyword stuffing. I'm adjusting my filters, too, but it's always an uphill battle...
@martinibuster: Thank you for the negative answer! I'm heart broken though: I thought I've finally found a reasonable explanation... In my mind the worst thing you can do was to host links to bad sites (even if not HTML-formatted in this case). Since my penalty is rather harsh (90% G* traffic is gone) I thought it made sense.
Well, I'm off to searching for something even more egregious than bad links. What that might be?!