When Twitter informs you that someone you respect has liked a tweet that's utterly moronic.pic.twitter.com/YEpkGM5Oca
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This is true for many of my likes. 
I think some also use Twitter "likes" as #1 a way of sort of "bookmarking" a tweet, #2 a way of acknowledging a tweet (when it is a reply to you), #3 a way of marking you've seen a tweet (to yourself).
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