Imagine the code asks to the reco engine for 5 items.
Since ezpublish filters out the recommended items based on their visibility/permissions/etc before displaying them, the result is that fewer items could be displayed.

Ideas for workarounds:

• hackish: always ask to reco engone for more items than needed (eg ask for 10). This does not guarantee that we will get enough items
• better but slower: if there are filtered items, keep sending requests to the recommender engine until you have enough