Well - you could try find the similarities or "document distance" of and between the Twitter users by matching their tweets against each other - kind of like the way one search for plagiarism, perhaps that might work. You could start by out by searching the tweets of a particular Twitter user - using some sort of application. If I am not mistaken - I believe Twitter does have something like this available - furthermore, comparisons between and of the groups against each other can be carried out, therefore that way we can get a comparison of the similarity or "document distance" of Twitter users.
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