Another client of ours is looking at integrating a site and demonstrated another theme for a different "paid" / "private" engine. The theme featured a popup for displaying to viewers of the website - when an item was bought. This was a neat feature that showcased activity on the website to viewers and also created a viewable product and link to the product they purchased. I wonder if this could be used as a form of unassisted cross selling.
I've included a picture.
See this link: http://i66.tinypic.com/sbsx2c.png
Perhaps this would ALSO be good fit with machine learning if that were also ever incorporated, where displayed recent purchases would be based on previous viewing habits of the user.