Our app's icon dates back to when shiny gradients were cool, so we asked users to design a new one, and about 20 different designs have been submitted.
A particular user submitted a very nice design, and several people asked her to make slight variations, so now she has 3 very similar variations of the same icon. If we do a simple "Choose the one your prefer" vote, then votes that would have gone to her concept will be divided by 3 (the 3 variations are evenly liked it seems), so her concept will loose, whereas without the variations her concept would probably win (see https://en.wikipedia.org/wiki/Independence_of_clones_criterion).
It is actually more complex than that: all submitters have reused ideas each other's ideas, so all icons share similarities. For instance, the icon(s) I talked about in the last paragraph have been forked and slightly edited and submitted as new candidates by other users.
It is great that everyone forks and that we get many variations, but this open source way of doing things means a simple voting protocol will not work.
Usage examples by actual open source projects (with the same goals) appreciated.