What if they expand the data by including reviews from people of second and third order of separation from the user? Each iteration would exponentially expand the data, and perhaps after four or five separations, you'd have sufficient data (though this may defeat the whole premise of getting data from your social circles)
But the further out you go, the lower the quality of the personal link.
What counts as a personal link, anyway? There are people on my Facebook profile I knew years ago in a different town, people on my LinkedIn profile I worked with 6-7 years ago. All people with whom I'm happy to stay in contact at a low level and retain in my wider professional network, but would I want to trust a recommendation from a similarly distant contact of theirs as much as I would a day-to-day colleague of my brother-in-law who I see every week? Probably not.
