Currently, if a person opts into the recommendations service in the Ubuntu Software Center but has not yet actually reviewed/rated any software, then zero results are returned by the recommend_me call. This has the the unpleasant result that Software Center hides the panel (this hiding is a side-effect of the fact that this code in USC is shared with the categories screen recommendations and with the current implementation it's a valid condition that there may be no uninstalled recommended items for any given category).
Anthony mentioned that this will change and a full set of recommendations will always be returned on opt-in once we start using the uploaded profile data, but currently it is the case. So, before Precise goes out, we will have to do one of:
1. Implement the ratings based on profile data functionality, such that a full set of recommendations are returned, or
2. We always return a full set of recommendations, even if they are initially somewhat generic as we continue to fine-tune the recommender.
Of course, a third possibility is to prompt the user to review/rate some items after opt-in for the case where no items are returned, but that doesn't seem a satisfactory user experience.
So, in summary, the goal is that we always return a full set of 60 items on a recommend_me call, and we fine tune that set as the recommender engine is tuned.