A professional photographer had some bad experience shooting for his relative's wedding event for free.
I empathise with his situation. Ultimately, commercial photography is all about creating images that satisfy your clients. You may create the most artistic and emotionally charged images that are lauded by fellow professionals, but if the very client does not like it, then the photographer has failed the assignment.
While clients who engage your services may be well aware of your style and what you deliver, their friends and relatives may not be aware. Come to think of it, you can roughly gauge the expectation from the way the people address you: "photographer" vs. "cameraman".
But which is worse: a photographer who doesn't take enough photos or a photographer who takes bad photos?
Looking from another perspective: he received the comments because he is their relative and they want to express their opinions openly. If this was another paid assignment, the relatives might have complained to the couple but they could have defended the photographer or even ignored their remarks, so such feedback never reached his ears and he would think that the couple and everyone else around them is happy with the photos. But we know that this is impossible: there are bound to be displeasure over some of the photos.
From the way I see it: the root problem is lack of communication: no clear requirement of the shooting style, no detailed itinerary for the photographer to standby at the locations.
I would take these incidents as learning experiences, but it does not stop me from offering complimentary services to friends and relatives. To me, the money is irrelevant to the whole saga: I believe the photographer would still get the same criticism if it was a paid assignment, won't he? My reward for covering weddings for friends and relatives is another opportunity to better my photographic technique via new experimentation and trying out new perspectives, and also a privilege to witness the celebratory event.