My favorite case where developers clearly missed the mark: Direct message on a tweet. You see a person in replies and decide to message them to discuss some private details. And there’s button for that! Right there. How handy!
Except that this button will ask you to select user next. What? Turned out, they built a button to send a _tweet’s content_ to _someone else_ inside a direct message. Why would anyone want that? Also, there’re about 3 other ways to let another person know about the tweet: @mention, retweet and, since recently, like. Are you sure, Twitter, we need a fourth shortcut for the same basic use-case?