I just saw a question by a user on SO that I thought was an exact duplicate from the same user. Looked at the user's questions and, sure enough, there was the same exact question. Unfortunately, the timing was such that I couldn't have seen it before. The user was a new user, which made me a little curious as to whether the user had somehow ended up with more than one account, so I looked up the user's name, "nitin" and found nearly a whole page of users with that or a similar id. Many of them with the same, exact gravatar and several others that looked very similar.
I know that these are generated algorithmically from user data, so I left a note on the latest question suggesting that the user get their multiple accounts combined. Now I'm scratching my head and wondering if I'm remembering correctly that identical gravatars indicate the same person. Is that correct?