Facebook said it's already aware of the potential for abuse. All of the paired conversations are private, and you still have options to block and report people.

Mentoring is only available for parenting, personal development and professional groups as Facebook ramps up the program. Other categories are due in the "coming months." You can't assume that Mentorship will be an option as a result, but this could cover many of the common instances where you're looking to give (or receive) some direction.