Pointless estimation: There are, say, around 10x2^(5x3) = Identicons assuming about 10 color shades can be told apart easily. That's ~300,000 different combin

Pointless estimation: There are, say, around 10x2^(5x3) = Identicons assuming about 10 color shades can be told apart easily. That's ~300,000 different combinations. You need ~650 people contributing to a repo in order to get a 50% chance of collision. So, while there are almost certainly collisions across all Github users, you're pretty unlikely to see one in any thread you'll participate in. Especially since so many Githubbers actually do have Gravatars.