It’s worth pointing out that it is extremely difficult to contact users on Twitter without an existing relationship. If your account isn’t followed by a user, the best you can do is @ mention him. I worked with a research team that reached out to some Twitter users to participate in a study. The response rate: 0%.
Twitter’s Developer Policies for Researchers, Archivists, and Librarians
Justin Littman
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It’s more complicated but not impossible. For example, Meredith Clark does research that puts her in direct contact with Twitter users. There are others.