Lots of library types use Twitter. I do. LISNews does. Jessamyn, Connie Crosby, Stephen Kellat, and so on.
And lots of people who are interesting to librarians use Twitter. For instance Leo Laporte and Robert Scoble are among the people I follow.
Still, some people just don't get why Twitter is so useful, cool, and just plain interesting. Perhaps this superb video from CommonCraft could help explain it.