The contact importer works both ways; so if A has emailed B, and A imports his contacts, A might get recommended to B as a friend. This is the usual explanation

The contact importer works both ways; so if A has emailed B, and A imports his contacts, A might get recommended to B as a friend. This is the usual explanation for mystery PYMK suggestions. That said, the algorithm for finding candidate pairs uses a lot of features, including past employers, schools in common, graph features other than just distance, etc. Occasionally it has a surprising success like this.