In my opinion, MatchBot is best when it's finding matches for inactive, orphaned, unsourced profiles.These profiles will never be improved without having attention drawn to them, and MatchBot does that. I just recently commented on a merge MatchBot proposed between two profiles with inactive managers, and one of the managers is now active & sharing wonderful stories about his grandmother.
MatchBot may not be leashed, but he is monitored, and I think more good than ill results (this was _not_ my opinion before becoming an MP!).
Cheers, Liz