The short article by Merton is worth a read. . . . if for no other reason than this: you should probably be doing something else and it will feel a little naughty to read an academic piece from 1968. See especially his section on the social-scientific pressures at work. I believe that this effect is relatable to a kind of memory distortion that I've called "mnemonic cross-pollination." If you are familiar with gezera shava, this will be old hat for you.
Legacy (a special kind of collective memory) can act like a tornado. A tornado can pull objects toward it and cast other objects off. In the case of a legacy like Albert Schweitzer or Jimmy Carter, the drawing force is the simplified, dominant narrative of their life. Some details don't fit quite well with the narrative (like Schweitzer's nationalism or Carter's theological anti-Judaism). These details are cast off until an alternative narrative emerges. The Matthew Effect, it seems to me, is the part of the mnemonic tornado that sucks. And, let's be real, tornados suck big time. St. Francis could very plausibly have said something like this:
composed). The legacy of St. Francis was such that certain "memes" continued to attach themselves to it long after he was dead. I talk more about this prayer in my book Historical Jesus: What can we know and How can we know it.
New Testament scholars have long wondered if some of John the Baptist's sayings might have come from Jesus or vice versa. In this case, the problem is even more pronounced because Jesus and John may have influenced each other. Another like example: if I listed all of the most memorable sayings of Jon Stewart and Stephen Colbert, would their fans be able to disentangle their legacies?
So now, let's have fun. Who can come up with the best Mark Goodacre saying that he didn't say? Remember, it must fit plausibly within the Goodacre legacy.