I never care about other readers' notes. In fact i find it annoying that you can't turn them off on the kindle. I don't care what other readers wanted to take note of, maybe because people read a book for different reasons and keep notes for different reasons (one may be doing research on a subject, another may just be collecting jokes). If that was a general case, Library books would be sought after for their side notes. There's little information there. OTOH the "people who bought this also bought" is sometimes useful, sometimes a recipe for very average reading.

To be fair the "friend network" recommendation are not much better either, but the trust factor involved makes us perceive them as more important.