By the way, apart from bias, there's also just the question of how useful this is.

For example, in the thread you posted above, nacin mentioned the "Customers Who Bought This Item Also Bought" approach from Amazon.

But I don't I think plugins really work the same way. If get a book on javascript from Amazon, I'm obviously interested in javascript and related programming languages. So you can show books on that subject and it makes sense. The fact that I install, say, XYZ SEO plugin doesn't really indicate that I want to see other SEO plugins, which are redundant, or that I want to see other plugins by the same author, which may be totally unrelated, etc. It doesn't really tell you much at all about what plugins I might want in the future.

I think for me, this approach just doesn't reflect how people look for plugins. I suspect (I could be wrong) that most people start out wanting specific functionality and they go to the plugins page and search for it. They don't usually go looking for a list of random but potentially interesting plugins they might try out.