There are other options besides social or text-based algorithms. My company, Pikimal, is pursuing one - we're pulling together facts on items and are allowing

There are other options besides social or text-based algorithms. My company, Pikimal, is pursuing one - we're pulling together facts on items and are allowing people to weight those facts to dynamically create recommendations. We've added some "user rating" facets but are just barely past our minimal viable product. I very much agree with you that social is limited. It's a filter which avoids spammers, but it also filters out experts and users. It also solves some of the problems introduced by the generic nature of search algorithms. I'm betting my time on the idea that the solution which wins will combine an understanding of the product space, the value of new features, a current understanding of price, and which can be customized transparently to the needs of the user.